Thanks for the quick reply!
Okay, I'm not sure if I could solder a serial adapter(weather should be cold&rainy on weekend so maybe I'll give it a try..)..but when I read your info, I think I should just be happy that this nightly works that good on the odd box as main functions are really okay.
Well, that reboot doesn't work properly could be an issue of the/my r69..on crappy original android there was no reboot option which forced powercycle to reboot too and on several armbians especially compiled for r69 it often didn't work either from card. At least just the armbian now on emmc reboots perfect..and for kodi on libreelec works a restart via ssh(not a reboot) to satisfy addons' wish to reboot to re-read configs after changing settings.
It would be nice to integrate the remote of the beelink(guess many users would appreciate that..). Maybe this is even helpful for me(could compare the codes with the file which works for that remote on other box). I thought remote isn't working , like the power led too because gpios aren't assigned properly in beelink dtb, similar to amlogics s905x/w where often basic functions are given with wrong dtb, but correct one brings more/all features. Is there a guide how to edit extlinux.conf?
I will test av audio and ethernet later. For me it is no problem that XR819 isn't supported, because a cheap(under 2€ shipped) 150MBit USB-Wifi does the job often better on all those cheap china boxes.
I'm really happy that after nearly two years this box is now a somehow quite usable mediaplayer!