====== Meddling with X displays over SSH ======
Since I use SDDM, the ''Xauthority'' file is located in a randomly-named file in ''/var/run/sddm''. To meddle with local displays, you can simply:
  $ export DISPLAY=:0
  $ export XAUTHORITY=/var/run/sddm/...

Now you can do stuff like ''xset dpms force off'' to turn them off, or open programs on them, or whatever.