Comment # 7 on bug 931296 from Wolfgang Bauer

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

There are still users complaining about this issue after upgrading to
Tumbleweed or Leap...
Latest example:
https://bugs.kde.org/show_bug.cgi?id=337470#c14