

The stuff you describe sounds like a cable timing issue. Not something you can fix in Linux. Think of it like the two devices trying to talk to each other on different frequencies and picking the highest res one that works. (so thats why they might get stuck on a random smaller one)
I had some examples like that in the past where some low quality or very long cables couldn’t reach it’s spec, even fresh out of the box, even on windows.
Oh, also I am pretty sure HDMI 1.3 does not do 4k at all. Either 1080 or 1440p was the spec limit.
If you can space the money for an experiment try an active DP 1.2 → HDMI 2.0 cable/adapter.
Maybe something like https://www.delock.com/produkt/85956/merkmale.html or Digitus branded. Depending on what known good cable manufacturer is available in your area.




Thats very interesting.
Do you maybe know if your gnome system was using x11 and your kde one is using wayland? Wayland might be a bit stricter when it comes to following specs and not implementing hacky workarounds. (or it could always be a bug)
Oh and if you do try out other cables, give us an update. I’m curious if it will work.