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Regain root after Marhmallow update?

I had Android 5.0 (PB1) and was rooted. I updated to Marshmallow using the posted method, and everything went well, but I did lose root access after updating to Marshmallow, which I did expect. I did downgrade to 5.0 (PB1) and tried to root using the posted directions, but to no avail. I am now attempting to update back to marshmallow. I also have a LOCKED bootloader.

Goto rooting the S5 thread as locked 6.0.1 is rooted for days now.
Killing Them Loudly

Molon-Labe said:
Goto rooting the S5 thread as locked 6.0.1 is rooted for days now.
Killing Them Loudly
Click to expand...
Click to collapse
So I still can root with 6.01 with a locked bootloder?

No, you cannot. This is discussed in numerous threads. Such as Muniz_ri's root thread and the unlock bootlooder thread. Please search before posting a thread which this has been mentioned. Thank you

Got to downgrade then root etc..
Killing Them Loudly

Molon-Labe said:
Yes look after method 4
http://forum.xda-developers.com/showthread.php?t=3337909
Killing Them Loudly
Click to expand...
Click to collapse
I read that article, but you need to be rooted do that, I tried to downgrade to 5.0 (PB1) and tried to root according to the directions from the link that is also referenced to on that page, but it did not work. Is there a specific way to downgrade to 5.0 (PB1) and to root? What iI did was I used Odin and flashed the PB1 image and then tried the rooting method mentioned, but it did not work. If there is a specific way to downgrade to PB1 and root, then I can follow the directions that you suggested to me.

Uptime73 said:
I read that article, but you need to be rooted do that, I tried to downgrade to 5.0 (PB1) and tried to root according to the directions from the link that is also referenced to on that page, but it did not work. Is there a specific way to downgrade to 5.0 (PB1) and to root? What iI did was I used Odin and flashed the PB1 image and then tried the rooting method mentioned, but it did not work. If there is a specific way to downgrade to PB1 and root, then I can follow the directions that you suggested to me.
Click to expand...
Click to collapse
i did this a bunch of times with my S5 with a locked bootloader (i have a Toshiba 11 emmc) --
flash stock PB1 and follow the Get Root instructions on PB1, http://forum.xda-developers.com/verizon-galaxy-s5/general/root-method-og5-ok3-t3290370
then follow upgrade instructions for locked bootloader to PD1. try this thread: http://forum.xda-developers.com/ver...ow-to-flash-custom-6-0-1-roms-locked-t3393943 (this worked for me)
( there is also this one, but it didnt work for me: http://forum.xda-developers.com/ver...w-to-update-to-g900voe1-5-0-keeproot-t3149784 )
All the info is here in the forums. good luck!

stras1234 said:
i did this a bunch of times with my S5 with a locked bootloader (i have a Toshiba 11 emmc) --
flash stock PB1 and follow the Get Root instructions on PB1, http://forum.xda-developers.com/verizon-galaxy-s5/general/root-method-og5-ok3-t3290370
then follow upgrade instructions for locked bootloader to PD1. try this thread: http://forum.xda-developers.com/ver...ow-to-flash-custom-6-0-1-roms-locked-t3393943 (this worked for me)
( there is also this one, but it didnt work for me: http://forum.xda-developers.com/ver...w-to-update-to-g900voe1-5-0-keeproot-t3149784 )
All the info is here in the forums. good luck!
Click to expand...
Click to collapse
I was initially on PB1 with root access, and looking back, I should have followed the link of how to unlock the boot loader and to update to PD1. Unfortunately, I followed the directions on the last link you gave me, the one you said that didn't work for you.....the one about updating to PD1 for locked boot loaders. Unlike you, it worked for me. I was on PD1 without a problem, but I wasn't rooted.. So I tried to downgrade back to PB1 and then follow the rooting directions, but it didn't work for me.
From what I have been told, since I upgraded to 6.0 (PD1), it is IMPOSSIBLE to downgrade to 5.0 and root. Is this correct?
Also, if that is the case, then is it possible for me to apply a pre rooted 5.0 image, so I can unlock the blootloader and update to 6.0?
Thanks in advance.

THERE IS NO ROOT FOR PD1 (MashMellow) for LOCKED BOOTLOADER yet. Once you're on MM 6.0 you will lose root. If you want root, you need to downgrade back to PB1 (LP), then get root working again. Once up upgrade from PB1 LP to 6.0 MM you will lose root.

buhohitr said:
THERE IS NO ROOT FOR PD1 (MashMellow) for LOCKED BOOTLOADER yet. Once you're on MM 6.0 you will lose root. If you want root, you need to downgrade back to PB1 (LP), then get root working again. Once up upgrade from PB1 LP to 6.0 MM you will lose root.
Click to expand...
Click to collapse
I am aware that once I got to PD1, I will lose root. I am also aware that I need to downgrade to PB1 and get root working again, but that is my precise problem. I have gotten back to PB1 flashing PB1 image, but I can't seem to get it rooted, at least not by following the directions mentioned on http://forum.xda-developers.com/verizon-galaxy-s5/general/root-method-og5-ok3-t3290370.
Question. After flashing back to PB1, do you I need to flash the PB1 bootloader? For some reason, I am unable to root when I get back to PB1.

Uptime73 said:
I am aware that once I got to PD1, I will lose root. I am also aware that I need to downgrade to PB1 and get root working again, but that is my precise problem. I have gotten back to PB1 flashing PB1 image, but I can't seem to get it rooted, at least not by following the directions mentioned on http://forum.xda-developers.com/verizon-galaxy-s5/general/root-method-og5-ok3-t3290370.
Question. After flashing back to PB1, do you I need to flash the PB1 bootloader? For some reason, I am unable to root when I get back to PB1.
Click to expand...
Click to collapse
You don't need to flash PB1 bootloader. Did you try install Kroot manually as suggested? Please show me where it failed? Did you run root.bat and if not working install Kroot manually and run roo2.bat.
Sent from my SM-G900V using Tapatalk

buhohitr said:
You don't need to flash PB1 bootloader. Did you try install Kroot manually as suggested? Please show me where it failed? Did you run root.bat and if not working install Kroot manually and run roo2.bat.
Sent from my SM-G900V using Tapatalk
Click to expand...
Click to collapse
I can tell you that when I tried to run the root and root2 batch files, I got a message that said the files were missing, so I looked at the root.bat file, and I ran the individual tasks in the batch file manually., including the manual install of king root. When I ran king root, it said no methods were available.

Uptime73 said:
I can tell you that when I tried to run the root and root2 batch files, I got a message that said the files were missing, so I looked at the root.bat file, and I ran the individual tasks in the batch file manually., including the manual install of king root. When I ran king root, it said no methods were available.
Click to expand...
Click to collapse
Try to run the bat files in regular mode too, not as administrator.
Sent from my SM-G900V using Tapatalk

buhohitr said:
Try to run the bat files in regular mode too, not as administrator.
Sent from my SM-G900V using Tapatalk
Click to expand...
Click to collapse
Thank you so very much!!! I ran the root.bat file in regular mode, and not as administrator, and it worked!!! I didn't think it would matter, but apparently it did. I now have root access on PB1. Unfortunately, I am unable to unlock the bootloader as I have a Toshiba 11 emmc.

Problem after flashing firmware and skipping Supersu

So recently I wanted to flash 20a via twrp on my G5 but it wasn't working. I reflashed 10i and my phone didn't want to boot up. So I decided to charge my phone after reflashing 10i once again without flashing supersu and I powered off the device and it turned back on with the "Your device is corrupt and it cannot be trusted sign" and so I tried to boot to recovery and my phone just factory reseted itself. I tried to boot into recovery with adb but to no avail. I even tried to flash 10d kdz and 10d tot both getting an error on LGUP and my phone is still stuck on firmware 10i. I even get an error when trying to update it with stock recovery. So now I have a phone with an unlocked boot loader and I cannot reroot again. Is there a way I can regain root? I knew I should have flashed supersu

RicardoSal24 said:
So recently I wanted to flash 20a via twrp on my G5 but it wasn't working. I reflashed 10i and my phone didn't want to boot up. So I decided to charge my phone after reflashing 10i once again without flashing supersu and I powered off the device and it turned back on with the "Your device is corrupt and it cannot be trusted sign" and so I tried to boot to recovery and my phone just factory reseted itself. I tried to boot into recovery with adb but to no avail. I even tried to flash 10d kdz and 10d tot both getting an error on LGUP and my phone is still stuck on firmware 10i. I even get an error when trying to update it with stock recovery. So now I have a phone with an unlocked boot loader and I cannot reroot again. Is there a way I can regain root? I knew I should have flashed supersu
Click to expand...
Click to collapse
I bet you didn't followed or read the 20a thread by autoprime nor did you bothered to read the TWRP thread as well. there's still a bug that prohibits you to downgrade from 20a unless you have a nandroid backup or a twrp recovery backup for the 10i. best option for now is to go back to 20a and wait for an update from the devs on fixing TWRP or try to follow the dirtycow method.

Jaistah said:
I bet you didn't followed or read the 20a thread by autoprime nor did you bothered to read the TWRP thread as well. there's still a bug that prohibits you to downgrade from 20a unless you have a nandroid backup or a twrp recovery backup for the 10i. best option for now is to go back to 20a and wait for an update from the devs on fixing TWRP or try to follow the dirtycow method.
Click to expand...
Click to collapse
The problem was that for some reason I couldn't update it but please pass the link to dirtycows :good:

RicardoSal24 said:
The problem was that for some reason I couldn't update it but please pass the link to dirtycows :good:
Click to expand...
Click to collapse
Look under the dev thread on autoprime topic about the stock N zips, if you read through last few pages you'll find all the links you need for recowvery to get root and twrp. Also if you're on 10i, why not just use lg up (make sure you either use older version or autoprime uppercut app) to flash 10D tot that already has twrp and then upgrade to stock 7 through twrp. Either way, all the info you need should be in last 3 pages of that thread by autoprime.
*** Edit ***
Just reread your post. If your getting errors flashing the 10D tot it's most likely due to you updating lg up, the .DLL, etc to install N. If so, uninstall lg up, and then download the lg up files and. DLL from the 10D thread. You can try uppercut app too as it's supposed to work between versions but I have not tested it myself. If all else fails then use the recowvery method.

jeffsga88 said:
Look under the dev thread on autoprime topic about the stock N zips, if you read through last few pages you'll find all the links you need for recowvery to get root and twrp. Also if you're on 10i, why not just use lg up (make sure you either use older version or autoprime uppercut app) to flash 10D tot that already has twrp and then upgrade to stock 7 through twrp. Either way, all the info you need should be in last 3 pages of that thread by autoprime.
*** Edit ***
Just reread your post. If your getting errors flashing the 10D tot it's most likely due to you updating lg up, the .DLL, etc to install N. If so, uninstall lg up, and then download the lg up files and. DLL from the 10D thread. You can try uppercut app too as it's supposed to work between versions but I have not tested it myself. If all else fails then use the recowvery method.
Click to expand...
Click to collapse
I've tried uppercut and I still get errors. I want to downgrade using the kdz file but the link is broken for me. Though I will try an older version of lgup. Thanks :good:

RicardoSal24 said:
I've tried uppercut and I still get errors. I want to downgrade using the kdz file but the link is broken for me. Though I will try an older version of lgup. Thanks :good:
Click to expand...
Click to collapse
Yeah not sure about uppercut. If you're still on 10i you should be fine using lgup to downgrade as long as you use the right version of lgup and h830 .DLL file. Also I'm not sure you can use refurbish option with kdz, but I know you can with tot. So maybe downgrade to 10D using tot and upgrade through twrp. If all else fails, use the recowvery steps on the above linked thread and you should be all good. Quick question, when you first start your phone, does it just show phone can not be checked for corruption or does it show the message can't be checked for corruption and visit this site... Etc. ? Reason I ask is the second message is updated bootloader and you won't be able to use lg up to flash MM firmware until you downgrade your bootloader.

jeffsga88 said:
Yeah not sure about uppercut. If you're still on 10i you should be fine using lgup to downgrade as long as you use the right version of lgup and h830 .DLL file. Also I'm not sure you can use refurbish option with kdz, but I know you can with tot. So maybe downgrade to 10D using tot and upgrade through twrp. If all else fails, use the recowvery steps on the above linked thread and you should be all good. Quick question, when you first start your phone, does it just show phone can not be checked for corruption or does it show the message can't be checked for corruption and visit this site... Etc. ? Reason I ask is the second message is updated bootloader and you won't be able to use lg up to flash MM firmware until you downgrade your bootloader.
Click to expand...
Click to collapse
Updated bootloader? I had no idea that was a problem. But since I'm on 20a i get the corruption message plus the link so O guess my bootloader is upgraded. How exactly DO you downgrade the bootloader?
I will mention that I'm stuck without twrp

RicardoSal24 said:
Updated bootloader? I had no idea that was a problem. But since I'm on 20a i get the corruption message plus the link so O guess my bootloader is upgraded. How exactly DO you downgrade the bootloader?
I will mention that I'm stuck without twrp
Click to expand...
Click to collapse
Okay since you have an upgraded bootloader and no twrp you will have to follow the steps in that post for recowvery which will give you Root and twrp. Once you have twrp, download the bootloader zip for whichever version you're planning on downgrading to (I.e. 10I bootloader if flashing 10i kdz) from autoprime and flash in twrp. You can also flash the complete zip (i.e. 10I complete zip) in twrp after flashing the 10I bootloader if you want to keep root and twrp (you will also have to flash SuperSU after flashing those files). But you can also flash kdz or tot with lg up after downgrading bootloader via twrp but you will lose root and twrp unless you flash 10D rooted tot.

jeffsga88 said:
Okay since you have an upgraded bootloader and no twrp you will have to follow the steps in that post for recowvery which will give you Root and twrp. Once you have twrp, download the bootloader zip for whichever version you're planning on downgrading to (I.e. 10I bootloader if flashing 10i kdz) from autoprime and flash in twrp. You can also flash the complete zip (i.e. 10I complete zip) in twrp after flashing the 10I bootloader if you want to keep root and twrp (you will also have to flash SuperSU after flashing those files). But you can also flash kdz or tot with lg up after downgrading bootloader via twrp but you will lose root and twrp unless you flash 10D rooted tot.
Click to expand...
Click to collapse
Can you please give the link to the thread you're talking about?

RicardoSal24 said:
Can you please give the link to the thread you're talking about?
Click to expand...
Click to collapse
The thread is:
http://forum.xda-developers.com/tmobile-lg-g5/development/stock-h830-20a-rom-flashable-zips-imgs-t3511294
If you're just trying to get twrp and root to downgrade look at the last 5 or so pages and look for the recowvery post. Once you do that visit:
http://forum.xda-developers.com/tmobile-lg-g5/development/stock-h830-10j-rom-flashable-zips-imgs-t3491363
and download the bootloader zip and then boot into twrp and flash the bootloader zip. Then you can use lg up to flash kdz file or tot file. If you want to do everything from twrp and skip lg up step just download the complete zip from the 10J thread and flash in twrp after flashing bootloader, then if you want to keep twrp and root make sure after flashing bootloader and complete zip in twrp flash SuperSU before rebooting.

jeffsga88 said:
The thread is:
http://forum.xda-developers.com/tmobile-lg-g5/development/stock-h830-20a-rom-flashable-zips-imgs-t3511294
If you're just trying to get twrp and root to downgrade look at the last 5 or so pages and look for the recowvery post. Once you do that visit:
http://forum.xda-developers.com/tmobile-lg-g5/development/stock-h830-10j-rom-flashable-zips-imgs-t3491363
and download the bootloader zip and then boot into twrp and flash the bootloader zip. Then you can use lg up to flash kdz file or tot file. If you want to do everything from twrp and skip lg up step just download the complete zip from the 10J thread and flash in twrp after flashing bootloader, then if you want to keep twrp and root make sure after flashing bootloader and complete zip in twrp flash SuperSU before rebooting.
Click to expand...
Click to collapse
Is there a video using the g5? I found only one and thats with the v20 and the guy in the video doesn't have much of a close up to his laptop

RicardoSal24 said:
Is there a video using the g5? I found only one and thats with the v20 and the guy in the video doesn't have much of a close up to his laptop
Click to expand...
Click to collapse
I don't think so but not 100% sure. If you follow the steps carefully you'll be fine. I didn't directly post the recowvery steps as I have not used this (I've had twrp and root since 10D). You can look on the v20 thread as it has a post for the v20 and our h830 recowvery method. Sorry I can't be more help with that specifically.

jeffsga88 said:
I don't think so but not 100% sure. If you follow the steps carefully you'll be fine. I didn't directly post the recowvery steps as I have not used this (I've had twrp and root since 10D). You can look on the v20 thread as it has a post for the v20 and our h830 recowvery method. Sorry I can't be more help with that specifically.
Click to expand...
Click to collapse
You were helpful enough :good:

Is it possible to flash TWRP recovery on a stock 20f phone?

I recently got this phone and updated the firmware to latest version, then I sim unlocked and bootloader unlocked the phone. I installed USB drivers, adb/fastboot etc.. but now I can't figure out what to do. I wanted to install TWRP to get lineageos running, however I'm running into an error when I try flashing TWRP recovery. I get this error "...FAILED (remote: unknown command)". I'm not sure why. II tried installing all different types of USB drivers, LG UP, LG Bridge.. everything. Is it simply not possible to flash recovery on 20f? Should I try downgrading to a previous version?

PhrostB said:
I recently got this phone and updated the firmware to latest version, then I sim unlocked and bootloader unlocked the phone. I installed USB drivers, adb/fastboot etc.. but now I can't figure out what to do. I wanted to install TWRP to get lineageos running, however I'm running into an error when I try flashing TWRP recovery. I get this error "...FAILED (remote: unknown command)". I'm not sure why. II tried installing all different types of USB drivers, LG UP, LG Bridge.. everything. Is it simply not possible to flash recovery on 20f? Should I try downgrading to a previous version?
Click to expand...
Click to collapse
you are literally spamming the threads with the same question everywhere.
please do your research before flashing anything.
no, you cannot flash recovery on 20f, you have to downgrade to 20A or 20C.

suhridkhan said:
you are literally spamming the threads with the same question everywhere.
please do your research before flashing anything.
no, you cannot flash recovery on 20f, you have to downgrade to 20A or 20C.
Click to expand...
Click to collapse
I posted 1 in this forum and 2 in another, i've been searching for an answer all day and didn't see why flashing doesn't work in 20f. After I downgrade and install with 20a, should I reinstall both 20f bootloader and modem or just modem?

PhrostB said:
I posted 1 in this forum and 2 in another, i've been searching for an answer all day and didn't see why flashing doesn't work in 20f. After I downgrade and install with 20a, should I reinstall both 20f bootloader and modem or just modem?
Click to expand...
Click to collapse
Read here....
https://forum.xda-developers.com/tm...ock-h830-20f-rom-flashable-zips-imgs-t3592855
https://forum.xda-developers.com/showpost.php?p=72127127&postcount=2

suhridkhan said:
Read here....
https://forum.xda-developers.com/tm...ock-h830-20f-rom-flashable-zips-imgs-t3592855
https://forum.xda-developers.com/showpost.php?p=72127127&postcount=2
Click to expand...
Click to collapse
Ok thanks. hopefully i won't run into any more issues (still don't understand why flashing doens't work in 20f though, oh well :highfive:

PhrostB said:
Ok thanks. hopefully i won't run into any more issues (still don't understand why flashing doens't work in 20f though, oh well :highfive:
Click to expand...
Click to collapse
Because the fastboot commands to do so we're always missing on this phone, just like they are on the g6. That's why we used to have to use sore rooted tot come file before dirty cow was found out. 20F has dirty cow patched, hence why you need to downgrade to 20A and go from there.

jeffsga88 said:
Because the fastboot commands to do so we're always missing on this phone, just like they are on the g6. That's why we used to have to use sore rooted tot come file before dirty cow was found out. 20F has dirty cow patched, hence why you need to downgrade to 20A and go from there.
Click to expand...
Click to collapse
that's really unfortunate. Are all new phones like that or just LG? the only reason I bought the g5 was because it had all the features I like: microSD, removable battery, IR blaster, and official Lineage support. None of the new phones have that
anyway on update on my progress: it looks like I finally managed to get TWRP working due to that recowery exploit. Tomorrow, I'm going to install Lineage as well as 20f modem/bootloader and hopefully won't have any more issues, thanks for the help.

PhrostB said:
that's really unfortunate. Are all new phones like that or just LG? the only reason I bought the g5 was because it had all the features I like: microSD, removable battery, IR blaster, and official Lineage support. None of the new phones have that
anyway on update on my progress: it looks like I finally managed to get TWRP working due to that recowery exploit. Tomorrow, I'm going to install Lineage as well as 20f modem/bootloader and hopefully won't have any more issues, thanks for the help.
Click to expand...
Click to collapse
Well, most new phones seem harder and harder to even unlock in general. As far as allowing unlock and removing fastboot commands, only seen that done with T-MOBILE versions of the G5 and G6.

suhridkhan said:
Read here....
https://forum.xda-developers.com/tm...ock-h830-20f-rom-flashable-zips-imgs-t3592855
https://forum.xda-developers.com/showpost.php?p=72127127&postcount=2
Click to expand...
Click to collapse
Ok i have unmodified LG G5 on 20f. im trying to get TWRP on it to install lineage OS.
i tried downgrading it to 20A using LG UP. but it says invalid KDZ file. Am i missing something

Root Guide for Lg G5 Tmobile on 20i Nougat?

So I've been doing a little bit of research, trying to figure out how to root my phone. I read I needed to downgrade my Security patch to something lower than 20i. I can probably figure out how to root it if I had a guide to downgrade my phone. Anyway I thought I'd ask this amazing community for some help! Thanks guys!

tuff3r said:
So I've been doing a little bit of research, trying to figure out how to root my phone. I read I needed to downgrade my Security patch to something lower than 20i. I can probably figure out how to root it if I had a guide to downgrade my phone. Anyway I thought I'd ask this amazing community for some help! Thanks guys!
Click to expand...
Click to collapse
Just follow the steps to flash 20a in that thread with LGUP. No other steps required. Just do a factory reset then flash 20a then root. If your phone is buggy after flashing 20a do another factory reset then root. After rooting you can follow the guide to flash 20i using TWRP.
Sent from my LG-H830 using Tapatalk

Sdobron said:
Just follow the steps to flash 20a in that thread with LGUP. No other steps required. Just do a factory reset then flash 20a then root. If your phone is buggy after flashing 20a do another factory reset then root. After rooting you can follow the guide to flash 20i using TWRP.
Sent from my LG-H830 using Tapatalk
Click to expand...
Click to collapse
Could you link what is the better steps to follow
I already try downgrade flash 20a with LGUP, without success.

eekthecat said:
Could you link what is the better steps to follow
I already try downgrade flash 20a with LGUP, without success.
Click to expand...
Click to collapse
Here is link for downgrading using LGUP
https://forum.xda-developers.com/tmobile-lg-g5/development/stock-h830-20a-rom-flashable-zips-imgs-t3511294
Here is alternative method for downgrading using lg Flashtool
https://forum.xda-developers.com/lg-g5/how-to/bring-lg-g5-to-life-download-mode-lgup-t3565508
Here is link for rooting
https://forum.xda-developers.com/tmobile-lg-g5/how-to/guide-root-twrp-lg-g5-using-t3580264
Tell me outcomes

dksoni411 said:
Here is link for downgrading using LGUP
https://forum.xda-developers.com/tmobile-lg-g5/development/stock-h830-20a-rom-flashable-zips-imgs-t3511294
Here is alternative method for downgrading using lg Flashtool
https://forum.xda-developers.com/lg-g5/how-to/bring-lg-g5-to-life-download-mode-lgup-t3565508
Here is link for rooting
https://forum.xda-developers.com/tmobile-lg-g5/how-to/guide-root-twrp-lg-g5-using-t3580264
Tell me outcomes
Click to expand...
Click to collapse
thank you so much

I have previously tried to root after I went to 20l but wasn't successful. I read about how I needed to downgrade to 20a, then root. However, I had errors when I tried to install the 20a KDZ file with LGUP. My bootloader is unlocked. Does anyone know if you can successfully downgrade and root from 20l?

Update, I was successfully able to downgrade from 20l to 20a, root, then flash autoprime's 20l zip via TWRP. Here is the shortened version of the steps I used.
1. Turn off virus scanner
2. Have latest SU, No verify zip, and 20l flashable zip on SD card
3. Factory data reset on current version (was 20l)
4. Developer options enabled
5. Turn on USB Debugging
6. Plug in to computer, prompt comes up on phone, accept
Do all the steps to unlock the bootloader (mine was already unlocked since I previously tried to do this)
7. Run “Upper Cut” (after LGUP installed)
8. “Upgrade” with 20a KDZ
9. Now on 20a, fresh install, go back in and enable developer options
10. Turn on USB Debugging
11. Plug in to computer, prompt comes up on phone, accept
12. Use Minimal ADB and Fastboot to run all the commands from this post https://forum.xda-developers.com/tmobile-lg-g5/development/root-h830-20a-nougat-lg-g5-hard-t3542496
13. While in TWRP, wipe data, install op sys, install SU and no verify zips.

Quick question, i am using t-mobile H83020i only GSM network, if i downgrade to 20a do i lose GSM unlock?
(I read a lot about people with that problem when downgrading)

T-Mobile LG G5 on stock Oreo (H83030c)

Is there a way to install a custom ROM on a LG G5 running stock Oreo? Can the stock firmware be downgraded to one of the stock nougat builds to help with bootloader unlock and TWRP install?

subaron said:
Is there a way to install a custom ROM on a LG G5 running stock Oreo? Can the stock firmware be downgraded to one of the stock nougat builds to help with bootloader unlock and TWRP install?
Click to expand...
Click to collapse
Yes, you can downgrade 30c to 20a, then unlock bootloader and install TWRP.

Is there a guide on how to do this? Thanks

I never found a solution to this and ended up getting a new phone. But that new phone just brokeand I am back to using the LG G5 again.
So now I am looking for a way to downgrade to 20a and the files needed to unlock the bootloader.
Appreciate any help provided.

subaron said:
I never found a solution to this and ended up getting a new phone. But that new phone just brokeand I am back to using the LG G5 again.
So now I am looking for a way to downgrade to 20a and the files needed to unlock the bootloader.
Appreciate any help provided.
Click to expand...
Click to collapse
Here this should help
https://www.youtube.com/watch?v=EOwYONhW0xE

subaron said:
I never found a solution to this and ended up getting a new phone.
Click to expand...
Click to collapse
Hi subaron what version are you on now? If you are on the latest 30C then you need to downgrade to 20A stock ROM first.
You must download the 20A kdz file and flash it with UPPERCUT. Then you enable Developer Options and can follow the info in this thread on how to install TWRP recovery and root. The only thing different from those directions is: instead of SuperSU, install Magisk.
Once you have rooted 20A with TWRP installed, then you copy the 30C COMPLETE .zip to the sdcard, reboot into recovery, and install that and install Magisk once again.