Nice :) In my new post I did try the current KF5 Kate on Haiku, too, works. https://cullmann.io/posts/kde-applications-and-icons/

Yes, not that nice, at least now it is re-opened.

It is not just available, both for Windows and macOS we try to get it to a good state and fix bugs. If that slowdown is reproducible, that should be fixed. But to do that, we would need more info, best would be to get some profile data for it.