See
https://bugzilla.redhat.com/show_bug.cgi?id=1515100.
I didn't have a problem when I upgraded a while back. I don't have F27 system
that
had been updated from F26. But FWIW the current /etc/pam.d/sddm-greeter file contains.
# Setup session
session required pam_unix.so
-session optional pam_systemd.so
-session optional pam_elogind.so
so the difference with mine is just those dash at the start of the
last 2 lines. Is this the same as commenting the lines?
F