New Plasma user here, so I’m not sure if this is the correct forum for bug reports with pre-release versions. Feel free to refer me to the right place.
Anyway, I’ve been testing Plasma 6 and Linux desktop progress in general since I heard that HDR is finally being implemented and there has been a lot of rapid progress on the gaming front. I have HDR working with a C2OLED but was obviously limited to 4:2:0 chroma at 120Hz with HDMI from an AMD 7900XT. (I believe the closed-source HDMI 2.1 Nvidia drivers support this?) So, I’m testing a DP → HDMI adapter from Amazon and to my amazement the adapter actually supports 4k@120Hz VRR. Unfortunately, Plasma (or Wayland?) gets stuck in HDR when I untick the HDR box when using the adapter. This does not happen with HDMI.
I’ve also tested the adapter with Windows and display-mode switching works as expected, so it’s not an adapter issue. I also noticed that the Windows drivers default to DSC, but I doubt there’s any relationship. Here is a photo to show what I’m talking about:
Note that display mode switching works fine going from SDR → HDR, but does not work in reverse.