Their distro seems somewhat confused.

According to kde.org/linux it comes with Flatpak and Snap. Distrobox and Toolbox. They don't seem to just pick a lane to be consistent, it's all kind of random.

It's at an alpha stage; it's reasonable to see what people will use, also because having an immutable base and needing tools to install things on top is still somewhat new.

KDE and Gnome are footing Flathub together and a lot of the community effort goes into Flatpak packaging.

I did not realize anyone outside of Ubuntu used snap. When I was on Ubuntu, I had many annoyances with snap, but not sure if they have since improved the experience.