I have been following Flatpak since the beginning of time, it is something that Linux users want, and it is appreciated.
But, it has a few flaws that are much needed.
It is impossible to work on a large creative project (animation, audiovisual production), if you don’t have the thumbnails in the browser.
Blender, GIMP, RetroArch are programs with a vital relevance in Linux. They need full support from Flatpak managers.
Many applications cannot access directories, you have to maneuver outside of the installation to use them correctly.
A permissions interface, iOS/Android style, would be timely for this.
Take these suggestions into consideration because they can be very beneficial to the project. Thank you for all your work.