Chewitt suggested I opened a discussion here before going to GitHub and so here I am.
On a NUC11TNKI3 (i3-1115G4) I am experiencing the following.
In Nightlies (tried today's) HDR10 content sees the screen "blank" intermittently. It's like the TV is temporarily losing the signal and soon after getting it back in a split second. On my LG TV (it's a C1 OLED) this has the HDR logo appearing and disappearing constantly in the top right corner, which is a clear indication of the signal getting lost and the getting connected soon after. I tested the stable release (12.2.1) and it doesn't happen.
On both Nightlies and stable I am also seeing video levels being output incorrectly. My TV is calibrated to 16-235, I activate "Use limited color range (16-235) under Settings/System/Display/General but if I play back both HDR and SDR material, black level is raised, obviously wrong looking. I used test patterns in both SDR and HDR to check and level 16 (for SDR) and 64 (for HDR), instead of being black, are perfectly visible as a dark grey (and even levels below 16, for SDR, and 64, for HDR, are clearly visible). If I disable "Use limited color range" in settings, black levels seem normal but the GUI displays with clear black crush.
As an extra element of information, using CroqueMr's Dolby Vision experimental builds (that can convert HDR10 to Dolby Vision), if I convert HDR10 to Dolby Vision levels appear correctly. I haven't tested with Dolby Vision patterns as I don't think I have them (I should look more thoroughly, though).
I remain available to provide logs or test whatever might be required.
EDIT:
The NUC is connected to a Denon X3800H AVR and from there to the LG C1. On the same connection an Ugoos AM6B+ has no problem outputting HDR10, nor displays wrong video levels. HDMI cable is supposedly of good quality (certified for HDMI 2.1 use).
