no graphical login screen for ppc64 f26

After ppc64 f26 install with "Fedora Workstation" software selection
that completed without obvious error,
and reboot, the graphical login screen is not displayed.

Problem reported at least on two openQA tests:
install_asian_language
install_european_language

Still have same problem if I simplify test with default language and no encrypted disk.

The /var/log data reported by this last test is saved in
https://michelmno.fedorapeople.org/graphical_ppc64_failure/