I am using Testing/Buster on my bare metal machine with systemd. Since some days SDDM (now version 0.15.0-1) does also here grey out the shutdown and reboot buttons. In a VM (with the same OS) the bug does not show.
This may be a race condition bestween the starts of systemd-logind.service and sddm.service, see https://github.com/sddm/sddm/issues/978 . The workaround provided there to start sddm after systemd-logind with a dependency entry works for me. Chris
