Comment # 9 on bug 995816 from Wolfgang Bauer

Autologin should work. 
It definitely worked on all fresh (KDE) installations I made since this has
been reported.

SDDM does not use any settings from /home/user either AFAIK.
And if that would have been the problem, changing /etc/sysconfig/displaymanager
wouldn't have fixed it either (as described in comment#0).

Feel free to reopen if it's still a problem in supported openSUSE versions.
Although it would probably be good to have exact steps to reproduce.