Yesterday, 09:17 PM
Flatpak (and snap) use virtual filesystems and give the application a very distorted view of the actual file system.
My personal recommendation would be to add a third folder in your regular directories (/home/franz/gimp/brushes) and use that. And then you discover that you can add the very same folder in both Gimp versions and so share brushes, patterns, palettes, etc... across your Gimp versions.
Also, if, in recent Linuxen, using flatpak or appimage maintains Python support in Gimp 2.10, with Gimp 3 some sanity has been restored and Gimp can use the system's Python3 installation and flatpaks/snap/appimages are no longer necessary. There are .deb for Gimp3 out there and they give you a more integrated Gimp experience.
My personal recommendation would be to add a third folder in your regular directories (/home/franz/gimp/brushes) and use that. And then you discover that you can add the very same folder in both Gimp versions and so share brushes, patterns, palettes, etc... across your Gimp versions.
Also, if, in recent Linuxen, using flatpak or appimage maintains Python support in Gimp 2.10, with Gimp 3 some sanity has been restored and Gimp can use the system's Python3 installation and flatpaks/snap/appimages are no longer necessary. There are .deb for Gimp3 out there and they give you a more integrated Gimp experience.