[LG G7 ThinQ  Guides, News, & Discussion] sirbow2:
UPDATE:

I kept finding bugs in josh1x's rom, so i installed the LOS17 GSI instead. Guide for that outline in reply #11

Figured this out and thought i'd write a simple tutorial that covers stock (i was at 20e) to lineage. You'll need the LG USB Drivers and adb/fastboot. There are a couple other things to download through out the tutorial and the unlock tutorial in step 1.

LG USB Drivers 4.2.0

ADB/Fastboot

LGUP with partition DL

Note: I was able to reach download mode and fastboot at any point in this process and even when it went wrong (kernel crashes, boot loops etc) while figuring out this tutorial. I found that i could just hold vol down or up in a bootloop with the usb connected to get to the mode i wanted.

Typical combos:

-Download mode: power off phone with usb disconnected. hold vol up and plug in cable

--NOTE: after wiping laf_a and boot_b, you must switch to slot b to access download mode (run command: fastboot -ab)

-fastboot: power off phone with usb disconnected, hold vol down and plug in cable. or adb reboot bootloader

--NOTE: after wiping laf_a and boot_b, you can only access fastboot from slot a by holding vol up on boot (for 20e/21d, on 11g vol down still works).

-Recovery: power off. hold power and vol down, when you see the white LG G7 logo temporarily release just the power button. Continue to hold power and vol down till you get to the option menu. Select Yes three times.

Guide:

1. Follow the universal unlock method here.

1.5. You need to zero out laf_a and boot_b before flashing 21d/20e to maintain fastboot access. Use adb to run the following commands

dd if=/dev/zero of=/dev/block/bootdevice/by-name/laf_a
dd if=/dev/zero of=/dev/block/bootdevice/by-name/boot_b

1.75. Enable usb debugging (should already be done). Open LGUP and connect to your phone. dont close it. If you open it after booting to DL mode it wont recognize it

2. 21d ULM firmware (here) must be flashed to use the latest twrp (20e works as well). The 11g twrp cannot install lineageos. I would imagine the EU firmware could be flashed as well, but I used ULM.

Boot into fastboot
fastboot -ab
Boot into download mode
Use the lg up linked in this post to flash 20e/21d without laf_a and boot_b with partition dl mode

3. Format userdata to decrpyt your file system so TWRP can access it. Then flash TWRP; boot_twrp-june.img can be found here. It's from Josh1x's post here. Note: this TWRP is non persistant.

Boot to bootloader
fastboot format userdata
fastboot flash boot_a boot_twrp-june.img
fastboot flash boot_b boot_twrp-june.img
Select restart in fastboot
Boot to recovery

4. Obtain the latest lineage build here. This is from Josh1x's post here. I attempted to flash gapps at this point and it failed, see the next steps.

Wipe everything
Transfer lineageos to your phone and install it
Restart normally

5. Gapps

Reboot to bootloader
fastboot flash boot_a boot_twrp-june.img
fastboot flash boot_b boot_twrp-june.img
Reboot to recovery
Transfer opengapps 9.0 to your phone and install.
Reboot to bootloader

6. We need to flash the stock lineage boot image (here) again now that we are done. The file was obtained with this method

fastboot flash boot_a boot.img
fastboot flash boot_b boot.img
Restart normally

if you have magisk, it would be magisk_patched_boot.img (here). this one was made from the above image with magisk on my phone.

fastboot flash boot_a magisk_patched_boot.img
fastboot flash boot_b magisk_patched_boot.img
Restart normally

Any time you want to flash something via twrp you will have to flash twrp via fastboot again (hence the non persistance), do your stuff in twrp, and then reflash the boot img (it will not boot if you dont do this or use josh1x's boot file). Just like steps 5-6 for gapps.

I am so glad to be off of stock, enjoy guys and girls!

Bugs (from my ULM phone)

-flash doesnt work in the camera. also probably why gcam crashes (gcam works on an EM phone somehow)

-brightness slider is calibrated incorrectly compared to stock. way too bright when set to 0%

NOTE: using ULM vendor fixed the flash and brightness, but gcam still doesnt work. This would make it the most functional rom for this phone at this point (vibrate does work).