I know there is the Plasma Addon for Firefox, and its damn great. Actually it simply does what Firefox on Windows does on its own, display download status bar, native notifications, and maybe some more things.
Not competing here, its great.
But afaik in the Snap native messaging already works, so I think the Flatpak should work too in no time. Using firejail breaks Firefox for me, and I dont want to depend on native nonfree codecs, so I think I will move there once done.
The same for Thunderbird, which I will absolutely not install natively, as it depends on Firefox ESR, I have no idea how the dependencies work there.
Do you know if and how it would be possible, to have such an addon work the same for Flatpak apps?
Also, different topic, do you think an Android-like popup for every major permission for flatpaks would be good? This would help a lot with permission control, as currently for example Edge Flatpak has horrible permissions and is not secure AT ALL.