I'm not able to get a new dm working. If I install lightdm or sddm no display manager works. It appears x starts, but all I get is a black screen with an underline cursor in the upper left corner. If I ctl-alt-f1 to console, startx works from there. I try dpkg-reconfigure and it shows lightdm is set. Once I install either lightdm or sddm, not even kdm works anymore, but removing those two allows kdm to work. only having lightdm or sddm doesn't work either. Not that I know about this, but I'm thinking it's something with systemd, one time on dpkg-reconfigure I got this message:
ERROR: /lib/systemd/system/kdm.service is the selected default display manager but does not exist
This is firestarter kde.