@beta Hello, since LG has stopped the unlock service since Dec 31 2021, I had to unlock using UsU. The bootloader was unlocked successfully, and it booted into android. The UBports installer reported no error. The recovery installed and all good up to here. Then after the installing update screen, it showed the Demigod SOC crash.
Somewhere in the very long UsU xda post, there is this:
Optional (not needed when you flash an UsU compatible ROM later) Flash the baseband package now: <model>_UsU_baseband_flash-in-twrp.zip
So the solution was to flash the baseband package in TWRP.
LG unlock tool (the post I referred to):
https://forum.xda-developers.com/t/unlock-unofficial-g4-unlock-any-lg-g4-device-with-usu.3760451/
Baseband package:
https://leech.binbash.rocks:8008/UsU/H815/H815_UsU_baseband_flash-in-twrp.zip