KDE Discover is the desktop/s package management tools for KDE akin to GNOME Software for visually managing the packages/software on your system. Grulich has been working on a Flatpak back-end for KDE Discover.
While it started out rough, Jan has been getting Flatpak integration going in Discover and currently supports most common functionality for Flatpak packages. There still is more work to tackle, but it appears to be taking shape quite nicely.
More details via Jan's blog.