This is probably a dumb question, and maybe there is a way to do this with native applications, but I can’t seem to turn on a screensaver. One with the funky art just to run for a few minutes or so to remind me, hey you left the computer on, don’t forget to finish what you’re doing.
In synaptic there is: gnome screensaver, cinnamon, kodi, mate, ukui, screensaver, and a few others. The last one, Xscreensaver, was the one recommended when I searched online but I also found a forum post where it was mentioned this was no longer maintained and not recommended anymore.
I guess a more broad question is how does an end user using Synaptic package manager know if the package is actively maintained or likely abandoned? Stale is ok, but it seems like using a project that hasn’t been updated in 15 years could possibly be a bad idea for security.
I see some relatively recent Xscreensaver releases, so that forum post might be wrong.
In any case, Xscreensaver’s animations (called “hacks”) are the best such collection for Linux that I know of.
I think they’re also supported by gnome-screensaver and mate-screensaver, in case those appeal to you. I haven’t checked KDE for compatibility (but maybe I should, since I prefer KDE).
Edit: By the way, Kodi is a media player/manager, not a screensaver.
Any program can be a screensaver if it changes the screen when the computer is idle.