Dear forum,
I’m having trouble with a Dell UP3214Q 32" 4k display connected to UHD-630 graphics (Intel i5-8500 integrated graphics).
The display can be switched between DisplayPort 1.1 (30 Hz only at 4k) and DP 1.2
When set to DP 1.2, I get a vertically split screen with two halves of a mirrored desktop next to each other.
It seems to be linked to LightDM. With GDM everything works fine out of the box. However, I’d like to run the vanilla Endeavour OS DE with XFCE4.
Thank you in advance!
No matter which Desktopenvironment you use, you’re not bound to a certain displaymanager. You can change it easily using the Welcome App.
That’s how I tried it out and found that gdm has no trouble running my screen at 60 Hz.
However, the appearance of my desktop changed completely. After I switched to gdm. Feels like I have to tweak a lot manually now - which I’d like to avoid, if possible.
Update:
It’s not the window manager. It’s the DE itself.
Gnome works.
XFCE4 gives me the split/mirrored double screen, also on gdm.
MATE doesn’t work at all. Just blanks the screen.
My problem is that I don’t like the non-usability of Gnome. At all. 
And KDE proved to be buggy and prone to crashes every time I gave it a chance.
Maybe running on Wayland??
Test the Xorg Gnome session to see if it works or fails too.
It’s not Wayland.
I’ve tried Garuda Linux with Wayfire and KDE. Both show the same split screen behaviour. But I could actually correct it into a usable state: initially left and right “halves” of the screen were reversed. After switching that I could use the DEs. That made me think about XFCE again.
And, voilà - same here. XFCE works if I just swap left and right screen areas (2160 vertical x 1920 horizontal each). XFCE on 60 Hz works. In a way.
I have no idea why Gnome could seemingly address the whole 3840x2160 screen area as one desktop, while all other DEs address it as a dual screen setup with two vertical desktops. I can of course stretch the panel over “both screens”, but it still feels a bit weird to run a dual screen setup on a single cable.