Comment # 6 on bug 105651 from Redsandro

I'm having the same issue with a 4K Dell UP2414Q with 3840x2160 as
1920x2160+0+0, 1920x2160 +1920+0.

Is it possible to do a workaround in xorg.conf, similar to nVidia's TwinView
and nvidiaXineramaInfoOrder as described in this question?

https://unix.stackexchange.com/questions/536175/how-do-i-tile-two-displays-onto-one-monitor-with-amd-graphics