default-displaymanager - auto mode
  link best version is /usr/lib/X11/displaymanagers/sddm
  link currently points to /usr/lib/X11/displaymanagers/sddm
  link default-displaymanager is /usr/lib/X11/displaymanagers/default-displaymanager
/usr/lib/X11/displaymanagers/console - priority 5
/usr/lib/X11/displaymanagers/lightdm - priority 15
/usr/lib/X11/displaymanagers/sddm - priority 25
/usr/lib/X11/displaymanagers/xdm - priority 10