Thought I'd give the LibreElec (Leia) v8.90.007 Alpha a go. I'm testing via a Denon UHD (HLG/HDR10/DV friendly) AVR and into a Sony UHD HDR TV. (XF9005 aka X900F)
Positive aspects in italics, negative aspects in bold
Frame rate and resolution switching via the the Whitelist works well - 720p output at 720p, 1080p output 1080p, 2160p output at 2160p.
CEC control worked with remote commands from my TV passed to LibreElec, and volume commands passed from LibreElec to my AVR.
2160/23.976p 10bit HEVC Rec 2020 HDR10 HDR content was output at 2160/23.976p 12-bit 4:2:2 Rec 2020 correctly flagged as ST.2084 EOTF (i.e.HDR10). However it looks like the HDR10 average/peak light level metadata wasn't passed (my HD Fury Vertex flagged them as 0/0)
2160/50p 10bit HEVC Rec 2020 HLG HDR content was output at 2160/50p 10-bit 4:2:0 Rec 2020 flagged as SDR, not flagged as HLG. (I've not seen any Kodi device flag HLG as HLG yet)
Audio passthrough of any bitstreamed audio caused nasty stuttering noise to come via my amp - rather than triggering the amp into passthrough. Disabling passthrough I got 48k/16bit PCM 2.0/5.1 etc. output
1080i25 H264 BBC One HD recorded native interlaced content from DSat (permanent 1080i25) was deinterlaced with the wrong field dominance so was very juddery, at least at times.
Watching Live TV SD MPEG2 576i25 native interlaced stuff seemed to be OK for the brief period I watched. Live TV HD H264 1080i25 native interlaced stuff seemed to drift between correct and incorrect field dominance deinterlacing