Comment # 9 on bug 931296 from Hrvoje Senjan

(In reply to Wolfgang Bauer from comment #7)
> Would it be an acceptable "workaround" if we run this on installing
> plasma5-desktop (or some related package) in the %post section e.g. to
> switch the PAM config to pam_unix.so?
> 
> pam-config -d --unix2
> pam-config -a --unix

Yes.