[T-Mobile LG G5 Guides, News, & Discussion] aquatic_snail_moss:
Hello from 2023! This guide still (mostly) works! The downgrade and recowvery method explanation in particular was a real lifesaver for me.

Here's some quick notes, including the condensed version of information already in this thread and a couple bits pulled from elsewhere. If you've already read through the whole thread, it'll mostly be redundant until you get to upgrading to the latest Lineage.

First, that downgrading method works at least up to 20k, which is what my phone had! Based on this video detailing the same method, it should work all the way up to 30c! You do NOT need Uppercut with the most recent version of LG UP.

"adb push twrp.img" doesn't specify a path. You'll want to rewrite it to:

adb push twrp.img /sdcard

Alternatively, you can do what I did in a fit of sleep deprivation and use the same path as the recowvery tools. Later, instead of /sdcard/twrp.img, just use twrp.img. It's not the right way to do this, but it did work.

At the time of writing, verity is 6.1.0 and the command needs to be adjusted accordingly. In general, when copypasting commands, doublecheck that they match the version you're actually using.

USE THE EARLIER TWRP, 3.2.3-0. If you don't, you'll get an Encryption Failed error. Don't worry, you can upgrade it later!

DO NOT immediately flash the current official build of Lineage!

First, flash the unofficial 15.1 build. It's no longer available at link provided, but can be found here:

https://xdaforums.com/t/rom-h830-h8...og-15-1-8-1-2020-build-by-bernie_nix.4059851/

It was thanks to this post in the original 15.1 unofficial build thread that I was able to find it. Fortunately, you don't need to-x86cpu.zip.

THEN boot up into lineage 15.1 and get ADB set up again (may not be necessary, but I did this to make sure I hadn't bricked my phone)

At this point you've accomplished what the original guide set out to accomplish, but if you don't want to stay stuck on 15.1 forever, here's how to get to the latest version of Lineage.

boot to recovery

wipe -> format data

use TWRP to flash lineage recovery, which is available along with whatever official lineage you get from the main website and will just be called recovery.img

reboot to recovery again

If you're stuck in a bootloop and adb cannot detect your device:

- take out battery

- hold vol down + power, let go of power when LG logo pops up then immediately press again

yes to factory data reset x2

this will get you to recovery

You should now be in lineage recovery! From here you can follow the official lineage instructions as follows:

do a factory reset

go back

apply update -> apply from adb -> adb sideload

in terminal: adb sideload lineage.zip

(replace lineage.zip with whatever version you're using; for instance, in my case the command was adb sideload lineage-19.1-20230510-nightly-h830-signed.zip )

adb sideload extras.zip

(replace extras.zip with gapps, root tool of choice, etc)

Because add-ons aren’t signed with LineageOS’s official key, Lineage Recovery will throw up a screen that says Signature verification failed. You can ignore that. Just hit continue.

Reboot and you're done!

I hope this is helpful to someone. Again, all of this information was already available here, on other XDA threads, or on the LineageOS website; I didn't figure this out by myself, just hunted down the puzzle pieces and consolidated them here. Thanks again for the help!

(edited for typos. feel free to let me know if there are any other typos or errors I should fix.)