He said (2023) it needs an extension protocol or per-compositor work - so screensaver support is available in KDE using the Screen Locker integration, just no port was done AFAICS.

A general "wayland" protocol for it didn't exist back then, but in this thread we see ext-session-lock exists now, and jwz was recently trying to use it where available: https://www.jwz.org/blog/2025/07/xscreensaver-wayland-and-lo... so you might see an xscreensaver port soon.