Users cannot log in using sddm on Fedora 23

[Andrej Podzimek]

>> After a Fedora 23 installation, users can't log in with sddm. A "login
>> failed" message is displayed by sddm, sometimes preceded by a short switch
>> to the tty and back.
>
> Anything recorded in these users' ~/.xsession-errors ?

No. :-( Nothing at all, it's empty. (Yeah, that was the first thing I checked.) Also "audit2allow -b" doesn't show anything related to sddm. But KDE works and starts just fine using startx.

Andrej