Where is it set then? I should be able to review the configuration somewhere on disk, right? If it’s set by a service, which one? There’s no “xserver”, “desktop”, or “gnome” service.
In a cinch ps aux | grep xserver.conf should work (and will work for any similar case where you don’t know what started your service).
systemctl status display-manager.service should contain the process as well, since it’s your display manager that is in charge of launching the actual X binary.
I’m running Wayland (XWayland according to xrandr), but all these settings are under config.services.xserver. Is the xserver part of that name simply misleading?
The difference is that I don’t know how X11 is launched when it goes through the wayland layer. With a “normal” X11 setup the display manager launches X11 with the -config flag to pass the correct configuration file through the xsession scripts, which is what services.xserver largely configures (though it’s not a very cleanly encapsulated module, it configures some kernel module settings and such too).
Obviously, this does not happen with wayland. I believe the compositor is responsible for launching however much of X11 it actually runs? If so, to set X configuration, you would need a gnome configuration option.
That said, I’ve not made my foray into wayland yet, so sorry, I don’t know how xwayland is configured. Maybe look through your ps list to see if you can spot an xwayland process and the gnome/gdm session scripts to see how this is concocted?