[Mount81]

Forgive me if this is a stupid question or if it's in the wrong thread, I'm kinda new with Kodi. 
On my Minix U9-H (both in Kodi 17.6 with Android and LibreELEC) 4K 10bit HDR material is output as YCbCr 4:4:4 (according to my Pioneer receiver) even if it's 4:2:0. Is that oke? In android I've set the display to 10bit 4:2:0.

 That's absolutely fine. Moreover the 444 output is the best in any case. The 420 has to be upsampled to 444 anyway (and than to RGB, but that's the business of your display) to be able to be displayed by your TV. So the upsampling directly to 444 is always better than when it's just being upsampled to 422 as it not involves any unnecessary intermediary step.