Hi, only to let you know:
After many problems with Lightdm, i switched to GDM and like the simplicity more.
The only weird thing is, since GDM, when logout from one user it isn’t possible to login in either users anymore. To login again, in one of the users, i have to reboot.
Boot with second screen connected freezes on two black screens.
Boot without second screen connected works but after connecting second screen, this one stays black. This on both Gnome and openBox.
But this i have to investigate deeper on this and the Arch forums.