There's a fair amount of overlap and collaboration in the engineering communities behind the different image-based/appliance OS projects, so it's not necessarily as redundant as you might think it is. E.g. the developers behind the distro tech behind KDE Linux, Gnome OS and Kinoite are pretty friendly with each other.

And of course the distros end up sharing the gross of the application packages - originally a differentiator between the classic distros - via e.g. Flatpak/Flathub.

One reason we're doing KDE Linux is that if you look at the growth opportunities KDE has had in recent years, a lot of that has come from our hardware partners, e.g. Slimbook, Tuxedo, Framework and others. They've generally shipped KDE Neon, which is Ubuntu-based but has a few real engineering and stability challenges that have been difficult to overcome. KDE Linux is partly a lessons-learned project about how to do an OEM offering correctly (with some of the lessons coming out of the SteamOS effort, which also ships Plasma), and is also pushing along the development of various out-of-the-box experience components, e.g. the post-first-boot setup experience and things like that.