Almost always, the version that gets into a release is the current stable version, as long as it has been available long enough for extensive testing. Debian Stable does not do bleeding edge. I would expect Forky to have KDE 6.something, probably 6.5, which has X11 as an option. 6.6 has been out for awhile, and it's still not even in the Debian Unstable repo, which is still on 6.5. I would be amazed to see no X11 option in Forky KDE.

