SOLVED: LightDM and xrandr
I use a script that is supposed to get executed when LightDM runs.
In /etc/lightdm/lightdm.conf , I have this:
display-setup-script=/etc/lightdm/monitors.sh
The script simply has the following:
#!/bin/sh
# Shutoff laptop display - use only HD monitor
xrandr --output eDP --off
xrandr --output HDMI-A-0 --mode 2560x1440
and is chmoded +x
This works in Debian and Arch but for the life of me, fails in Artix. Just a black screen.