Kubuntu should now be fully ready for this. In fact, on latest Questing daily ISO we no longer install the Plasma X11 session by default. It can be installed for users who want it via the package plasma-session-x11.
Rationale is that it is highly improbable that we can support the X11 session in 26.04 LTS (or now even), so like Ubuntu desktop it is probably better to rip off this sticking plaster in 25.10 and concentrate on wayland with less distraction.
I’m starting to get really excited for the next LTS. There’s going to be huge changes. Might have to reinstall the whole thing though just to be safe.