Discover: restart for system updates: no restart

After non-system updates, including Firefox and Freedesktop, I accepted the invitation to restart:

Discover remained on screen, without its window.

I keyed Control-Q, there remained a black screen.

I switched to /dev/tty3, ran htop, then filtered to confirm that neither KWin nor plasmashell is running.

Without filtering:

  • /usr/bin/plasma-shutdown is running.

Nothing matching at https://bugs.kde.org/, as far as I can tell. Before I report:

  • whilst the machine is in this state, should I do anything more to diagnose?

I don’t know whether this bug will be reproducible, I do have a VirtualBox snapshot that preceded today’s run of Discover:

I’ll use shutdown(8).

Environment

Kubuntu on Ubuntu 25.04 (as a VirtualBox guest).

System settings: apply system updates after rebooting.

Done.

The subsequent restart routine succeeded.

IIRC the bugged routine did not have the pictured countdown: