I just stumbled across AndroidTV on x86 and found these builds: https://archive.org/details/androidtv-x86 the 32bit build (android 8) works well. I've installed it on an old dell E5470.
Working:
Not working:
In order to get the 4K output, I had to make changes to a couple of files. I edited the android.cfg grub config file to force only HDMI output. I also added a new kernel boot param 'hdmi_audio' to be used by the second modification needed.
The second was /system/etc/init.sh. In the function to set up the hal audio, If the 'hdmi_audio' kernel param was provided, the hal audio output was set to device 3 instead of the default device 0.
If you want specifics, I can provide.
This is still basically the only way it's done.
https://www.xda-developers.com/android-tv-x86-repurpose-pc-media-streamer/