Comment # 2 on bug 963321 from Antonio Larrosa

You can see the stdout/stderr of sddm by running:

journalctl -u sddm

What version of sddm are you using? is this a normal Leap update or did you get
it from obs/somewhere else?
Can you add a couple of attachments to this bug for the output of rpm -qi sddm
and the contents of /etc/sddm.conf ?

Are you starting sddm manually? or running "systemctl start sddm" ?