So it seems that not only could there be a Kodi/Librelec growing pains. It could also be my hardware. I checked my TX-NR787 reciever and according to the specs, all HDMI inputs are HDCP2.2 compliant.
https://www.zkelectronics.com/receiver/onkyo-tx-nr787/
BUT, I then came across a post explaning the differences between HDCPv2.2 and HDMIv2.0. There was blurb in that that referred to Onk's units;
https://www.audioholics.com/hdtv-formats/hdmi-2.0-hdcp-2.2
This to me is bullsh!t. Manufacturers shouldn't be allowed to pull this kind of stuff and still get certification with the licensing bodies. Either they stick to the spec or they don't get certified to show the logo.
I have Onkyo TX-NR646 (launched in 2015) and I suspect that this HDMI bandwidth limitation definitely affects my model. It seems like that I have to turn off support for more than 8 bit per color channel in order to have proper audio pass-through when utilizing dtsX or Dolby TrueHD (Atmos) in combination with 2160p 23.976 Hz video.
If I leave the default support for 12 bit per channel enabled, the receiver indicates that it is showing RGB 36bit 3840x2160 23.976Hz video. The issue is that when the sound channels are utilized intensively (action scene with a backing soundtrack), the sound will cut out for a second or two, and then come back on as if nothing happened. This is very jarring and usually happens in the most annoying moments.
This does not affect other audio formats, only dtsX/DTS.MA and Dolby Atmos/TrueHD, and only when using 36bit 3840x2160 23.976Hz video. If I turn off Deep Color support on the receiver or use non HDMI 2.0/HDCP 2.2 ports, the video is shown in 24 bit color and everything works just fine. They probably didn't expect 36bit RGB UHD video when they made this design tradeoff
I think they may have fixed this issue by the time your model came out (2018).
Display MoreWell, black screen and no signal .... this as soon as 10-11sec auto start booting (syslinux menu is displayed, showing 5 seconds to start live) and mini-PC still running, no reboot at all, stuck in "no signal" on screen, must be shut down by long press on power button.
This only appears when the TV(dolby vision capable) is defined as EDID 2.0, ie 2160p @60, which is verified as 'bubbled' when powering ON the mini-PC.
BUT when defined as EDID 1.4, power-on is then bubbled 2160p @ 30 on TV and LE 20230331 starting after 10-11sec on live, then it take control of the display with another 2160o@30 bubble showing in the 2 sec, then immediatly appears the LE Welcome screen !, and everything is fine.
Also I just tried Ubuntu 2304, same problem at 4K60hz with native boot, then only booting on '(safe graphics)' option, while native default boot is ok as soon as downgraded to 30hz.
As i saw on reddit & other unix forums that some problems were related to AdlerLake 12thgen intel, may be within i915 or others points.
And as I will receive soon two other Adler Mini-PC, so two other bioses, i will diagnose if it could be my ACE Magician bios that could be buggy ... But note also that a W11 22h2 to GO key gives all the best, leting better think a software problem (in driver made by intel for open world?).
See you later ...
This may be a HDMI cable issue. I checked the necessary bandwidth for image transmission with resolution of 2160p at 24bit per channel and you only have enough bandwidth for 68 frames per second at max HDMI 2.0 capacity. Adding in audio transmission and you are at full capacity at 60 Hz. I would get a HDMI 2.1 compliant cable and try it to see if this is the problem.
HDMI v1.4 and HDMI v2.0 cables are wired identically, and if you use short cables (under 2 m) you could probably get away with using a HDMI v1.4 cable. But just to be safe, get a decent HDMI v2.0 or v2.1 cable and avoid the hassle.