I'll just say this is a good reason to use a full DE like Gnome or KDE. At least with Gnome/X11 I never had any issues with external monitors. And it seems to a

I'll just say this is a good reason to use a full DE like Gnome or KDE. At least with Gnome/X11 I never had any issues with external monitors. And it seems to always remember the display config of any monitors I had used in the past.