They don't want you to use the full Ubuntu package repos nor any PPAs, though. They expect you to be content with just KDE apps and Flatpak. Flatpak in no way covers my needs on its own, and I got tired of fighting with 3rd-party repos on it. If I have to run Ubuntu and want up-to-date KDE, I run Tuxedo OS. That's what my work laptop is on, and has been pretty great overall. The rest of my machines are on one rolling release or another (Debian Testing, OpenSUSE Tumbleweed, or Arch).