Add-on listing confused with flatpak branches
gnome-software listing add-ons from Gimp Flatpak is confused because it doesn't check the branch / version match.
The 3 GMic you see, one is the old version (not usable), one if the right version, one is the version of Gimp beta on flathub (2.99).
It's even more confusing that there is no indication of which is what.
Without looking at the code, but by checking the behaviour, I can suspect that the root cause is like for #1020 that gnome-software should use flatpak to list the available extension/add-ons for a package rather than rely on the .desktop. And then check for the version / branch matches.
Related https://github.com/flatpak/flatpak/issues/4208 and https://github.com/flathub/org.gimp.GIMP/issues/105
Edited by Hubert Figuière