Not sure if this community is still alive but just in case...

I noticed today that my app menu and applet shortcuts to start GIMP/photoGIMP weren't working. A quick visit to the photoGIMP repo and someone has posted the fix (all credit goes to UniverseLord for this fix).

I originally installed GIMP via Flatpak so mileage may vary. Anyway, close photoGIMP/GIMP if its open.

Go to ~/.local/share/applications/ and make a backup copy (just in case) of org.gimp.GIMP.desktop . Now edit that file (not the backup file) and look for the line:

Exec=/usr/bin/flatpak run --branch=stable --arch=x86_64 --command=gimp-3.0 --file-forwarding org.gimp.GIMP @@u %U @@

and change 3.0 to 3.2 so the line reads:

Exec=/usr/bin/flatpak run --branch=stable --arch=x86_64 --command=gimp-3.2 --file-forwarding org.gimp.GIMP @@u %U @@

Save that file, close it and photoGIMP should now open fine.