Unix like systems with X11 or Wayland All Unix like systems with either X11 or Wayland are well supported since ever.
Linux with X11 and now Wayland is for a long time the primary system on that Kate work happens.
Over the years it was, like most of the KDE applications, ported to various BSD variants.
Be it some mainstream Linux distribution like Fedora or a niche one like NixOS, Kate is available as binary package.
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.