How do I really prevent sleep?

Lately (this year) I have noticed that my Mac mini will sleep even if I have instructed it to never sleep. It runs server processes for me (Monterey with Server.app) and it should simply never ever sleep. But since a few updates I have noticed the system goes to sleep anyway (I can see this in ARD).

This seems a bug, but maybe there is something I can do (without anyone being logged in all the time, which is also true after an unattended reboot) that prevents my 'server' macOS to go to sleep?