I have an issue with playback of any 2160 content on my Beelink GT1 (S912), running Coreelec 9.2.6 official, and this issue was on as well in any of previous versions.
So as soon as I try to playback some mkv 2160 file, video output blacks out, so I have to restart device with remote, as I loose display output. I have a kodi.log made on this, available on https://file.io/UZqx20A4tW6f
(I cannot attach log here as am a new user). If somebody investigate please look starting of playback of file :OnPlayMedia /storage/videos/For.All.Mankind.S01E01.2160p.WEB.h265-PETRiFiED.mkv
Any kodi option was/is pretty default, have pasted outputs on http://ix.io/2SB2
I have tried already to whitelist all resolutions, or all resolutions but first two, as well as tried other advices (turn of sync on start/stop etc), yet no good for me - whatever I try, all I get after starting playback is the blackout screen.