Trying to run KDE 6 Plasma with Wayland....

[Maxnix]

There's a PR open on the sddm issue.

296052 – x11/sddm: Wayland session login bounces with exit 125 on FreeBSD 15.1-RELEASE (ConsoleKit2)

bugs.freebsd.org

Thank you, but I already know about that bug, and already have a patched version compiled locally.
Maybe it needs to be recompiled, will give a try.