Most likely an adapter issue, some failure in communicating the possible resolutions through the HDMI/DP conversion.
Can you find a flex io HDMI port on eBay? Just make sure you get the right version of the flex io card. That's the most "supported" way to deal with ports, but it's more expensive than a simple adapter cord.
Looking online I only see G4 (and maybe later) ones. But thanks for the tip.
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.
Replying to your comment again to say the cable worked. I could buy this exact cable, and my OpenSUSE Leap/KDE computer now does indeed work with 4k60hz on my TV.
Sadly, the processor isn’t really up to the task. But it was a bit of a shot in the dark anyway, I pretty much just hoped it’d work. But 1080p does do well, and on YouTube I generally watch 1080p.
I’ll try xfce next to see how that runs.
to me that smells like what I said in the other comment:
Wayland might be a bit stricter when it comes to following specs and not implementing hacky workarounds. (or it could always be a bug)
I feel like, if a cable is high quality and up to spec, it will work with wayland. But if the signal integrity is below spec, wayland might fall back to slower signaling while x11 is more lax and ignores the issue and so a worse cable still works even if unnoticably below spec quality. Or the 4k over hdmi 1.3 is some hack that x11 supports and wayland doesn't because it's out of spec.
But thats just a feeling. May be wrong.
Thanks for reporting back with your findings!
I don’t mind spending another €20. I’m pretty happy with my little computer costing only €100, including RAM and SDD.
Oh, also I am pretty sure HDMI 1.3 does not do 4k at all. Either 1080 or 1440p was the spec limit.
I didn’t think so either, but in Gnome it (at least this cable) did, like I said. I could easily tell and it said so in the settings.
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.
It seems to be the other way around. I reinstalled Gnome yesterday to test the HDMI 1.3 cable thing, and XDG_SESSION_TYPE is Wayland. And I’m pretty sure my KDE install didn’t have Wayland.
What distro btw?
OpenSUSE Leap
Maybe try kscreen-doctor? I don't use kde regularly but that showed up in a search.
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