[LG V20 Guides, News, & Discussion] |bogdan:
Hey there!

First of all, let me thank [MENTION=2881807]x86cpu[/MENTION] for his sustained efforts to support this device, and to finally get it to LineageOS official status!

I have this working on my LG V20 H990DS SEA. I flashed it coming from unofficial LOS 15.1, using the following procedure (in a bit of detail, for my future reference, and maybe it will help others, too):

backup apps using TitaniumBackup (it's not my daily driver, so not that important, but I did a backup, just in case)

reboot to recovery (I have TWRP 3.2.3-0)

format "Data", wipe "Cache" and "System"

use ADB sideload to flash "lineage-17.1-20200410-nightly-h990-signed.zip" (the ROM), "open_gapps-arm64-10.0-nano-20200408.zip" (required if you want Google Play Store, which I guess we all do :) ), and "Magisk-v20.4.zip" (optional, if you want root, which again I guess most of us do); flash all 3 one after the other, with no reboot or any other action in-between

reboot to system, wait for the setup to start; the first boot after an update always takes longer (I guess because of the "optimizing apps" step)

setup phone

to solve the "ctsProfile: false" / "Device is not certified" in Play Store issue, I installed "MagiskHide Props Config" and "Busybox for Android NDK" Magisk modules, ran "props" in a su shell, and followed the steps to set the device fingerprint to "LG V20 H990DS" (I don't really get why / how this works, it's basically the same phone, but as long as it works...)

What works (which I explicitly tested for):

Wi-Fi, bluetooth w. aptX

second screen (I was used to LOS 15.1, so this came as a big surprise!)

both SIMs, 4G mobile data

fingerprint

camera (only tested with the default camera app, it was quite laggy last night, in low light, now it's a bit better)

OTA update from Settings -> System -> Advanced -> Updater

Issues:

- [low] "Network traffic monitor" doesn't show in Settings -> System -> Status bar; turns out that it's been disabled for devices with a notch (https://review.lineageos.org/c/LineageOS/android_packages_apps_LineageParts/+/238702), so I'm guessing the second screen somehow counts as a notch?

ended up using "Network Monitor Mini" instead

[low] some weird data (negative values & stuff) in System -> Battery -> "Battery usage" view; not very important, let me know if you want to look into this and I'll get back with more details

[med] Hi-Fi DAC not detected (looks like the kernel module is missing - ALSA only sees the chipset msm8996tashasnd soundcard)

[med] 2.4GHz Wi-Fi is very slow (~200kbps) when playing music over bluetooth headphones, gets back to normal when I turn off bluetooth

5GHz Wi-Fi works fine either way

[HIGH] once in a while it gets completely stuck with a black screen, where I need to force-reboot it by pressing Power + Volume Down for ~5s (or take out the battery)

it happened 5-6 times, twice after I did the OTA update to latest nightly (20200411)

I have a feeling it's related to reading the fingerprint, I'll try to not use the sensor for a while and see if it still happens

any pointers to how I can debug this?

I mostly use it for audio (hence the Hi-Fi DAC not working is unfortunate, but I got used to it), so if you want me to test anything else, let me know!