I have a high-res monitor that requires two links to feed it because a single link cannot manage the bandwidth. Since there are a total of about 2 monitor models ever that work this way, this has, unfortunately often been a poorly tested setup causing similar problems.
To make this work, I have to tell the Nvidia driver to lie about the screen layout and present the two monitors as a single screen via Xinerama info:
Option "TwinView" "True" Option "ConnectedMonitor" "DP-0, DP-2" Option "NoTwinViewXineramaInfo" "True" Option "nvidiaXineramaInfo" "False" Option "MetaModes" "DP-2:2560x2880 +0+0, DP-0:2560x2880 +2560+0"
Unfortunately, to make Xinerama work on modern Xorg, RandR has to be disabled, so I have these parameters patched into my Xorg wrapper script:
-extension RANDR +xinerama
This worked fine as a workaround for years, but recent releases of KDE (I am on EL9) have stopped working. Latest that works for me has been 5.24.6. 5.27.x segfaults immediately.
If I remove those options from my Xorg wrapper, it works, but my desktop is split in half and my monitor works as two distinct monitors, which makes for a rather poor user experience.
Can anyone suggest a workaround for this? Either to make plasma not segfault with RandR disabled or to get RandR to lie to it everything and expose a single stitched-together monitor?