joinski i was feeling it !
I would be glad to help but my skills are limited...
I have two nucs on which i can generate logs, make tests, etc...
One is on Celeron J4005 and one on I3 8109U.
Partially solved the sound problem with these commands :
mount –o remount,rw /
cp /var/lib/alsa/asound.state /recalbox/share/system/asound.state
echo "alsactl restore –f /recalbox/share/system/asound.state" >> /etc/init.d/S99custom
And partially solved the compatibility with 4K TV's with this :
cp /etc/X11/xinit/xinitrc ~/.xinitrc
xrandr -s 1920x1080
Have a good evening.