GDM provides a way for a system to specify whether it wants wayland by default, xorg by default, or the old RHEL style of Xorg running as root and shared between the login screen and the user session.

The latter option is specified by setting

PreferredDisplayServer=legacy-xorg

in the [daemon] section of the GDM configuration file. Unfortunately, this option doesn't currently work. It needs a small 3 line change:

~~~

+        if (self->display_x11_authority_file != NULL)

~~

to the gdm_session_get_display_mode function to work.