Comment # 5 on bug 1170443 from Rainer Klier

(In reply to Frank Kruger from comment #4)
> I do not experience your issue with TW20200422. Anyway, what is the result
> of 'su -c whoami'?

rainer@lap051-linux:/> su -c whoami
Passwort: 
su: Fehler bei Authentifizierung

journalctl --reverse gives:

Apr 24 21:42:45 lap051-linux su[12443]: FAILED SU (to root) rainer on pts/20
Apr 24 21:42:43 lap051-linux su[12443]: pam_unix(su:auth): authentication
failure; logname=rainer uid=1000 euid=1000 tty=pts/20 ruser=rainer rhost= 
user=root
Apr 24 21:42:43 lap051-linux unix_chkpwd[12445]: password check failed for user
(root)
Apr 24 21:42:43 lap051-linux unix_chkpwd[12445]: check pass; user unknown