Comment # 2 on bug 1052268 from Dr. Werner Fink

As my systems here around as well as my private systems with 42.3 do shutdown
with poweroff you might specify more information to enable the maintainers of
systemd to help you.

Specify the exact hardware/mainboard and firmware/bios type and version.  Also
please check if on the shell prompt, after becoming root, the following comand
sequence does do the shutdown with poweroff:

   shutdown --poweroff now

simple to check if this is a systemd problem or a problem of the used display
manager and/or desktop environment.