Comment # 6 on bug 955471 from Wolfgang Bauer

(In reply to Wolfgang Bauer from comment #4)
> Ok, I noticed now that there are indeed no themes available for selection in
> Leap, it works fine on my 13.2 system though.
> I'll have a look at this.

Hm, actually it seems to be a bit random whether the themes are displayed or
not (on 13.2 too).
And I noticed that if it doesn't work, also the preview in the SDDM settings
module doesn't work after you entered the screen locking settings.

With a bit of experimenting, I found out that it reliably works after you enter
the "Workspace Theme"->"Look And Feel" module, which has a similar theme
selection widget.

So this doesn't seem to be a packaging problem at least.
I'd rather think it's an upstream bug (something not being initialized
correctly?), but I'll try with another distribution first before reporting it
to KDE.

I do remember similar problems in other setting modules in earlier Plasma5
versions, but most of them seem to be fixed meanwhile.

@Armin Mohring:
Could you please clarify what problem you have with the lock screen background?
As indicated, this works fine here.