Please provide Flatpak / Flathub

[wcasanova]

https://docs.flatpak.org/en/latest/introduction.html
having a flat package ensures correct operation on any linux distribution, which makes it even easier to maintain.
Every day, more and more apps like flatpak are added, software like Kicad has been packaged as Flatpak for some time now.
This is also helpful for users of Fedora Silverblue and immutable systems.

https://beta.flathub.org/statistics

[MattSturgeon]

It makes sense to add a flatpak manifest to the repo, or at least a build-aux/flatpack/ script to generate one from cmake.

Ideally, the app manifest would be committed to the repo so that gnome-builder and similar IDEs can use it to build OBV, but if possible we should still avoid duplicating stuff like version number, shared/system dependencies, etc.

Some projects commit an auto-generated flatpak manifest and use git-hooks to re-generate it automatically every time you commit. Flatpack supports /* comments */ in JSON so we could do this and insert a comment along the lines of "auto-generated by (script filename). Do not modify".

To get on flathub, someone willing to maintain the package would have to submit a PR to their GitHub. If we have an app manifest upstream (here) then maintaining a flathub package should be pretty low-effort, especially since they have a system that checks for upstream releases and proposes PRs on the flathub repo

EDIT: Even if we don't add a flatpak app manifest upstream, here, it should still be straightforward for someone to produce their own and get it added to flathub.

If there's anything we need to use libportal for, to work properly in sandbox environments, I'm sure PRs would be welcomed.