Splitting a physical screen using xorg.conf?

In linux, is it possible to split a physical screen (vertically) in multiple virtual screens, using solely xorg.conf ? I know that xrandr supports this in theory (through the “monitor” feature, eg, --setmonitor), but gnome/gdm doesn’t support that so it’s not helping.

My use case: split an ultrawide 3440x1440 monitor in 2, one part 2580x1440 and one part 860x1440.


No. There once was fakexrandr but that only worked for xlib based applications.