Logout command does not work

I want to get the computer to turn off after a certain amount of time. There is only a suspend option in the power manager, so I want to run the shutdown command by the screensaver.

The command entered in Lock Screen -> Logout -> Logout command in the screensaver settings does not run. I tried the following commands:

shutdown
/usr/sbin/shutdown
notify-send --urgency critical 'test message' 

See https://forum.xfce.org/viewtopic.php?pid=60174#p60174 for details.

Versions

• xfce4-screensaver 4.16.0 (from ppa:xubuntu-dev/staging)
• Ubuntu 20.04