Consider upgrading/ maintaining flatpak in LM #517

Flatpak plays a central role in Linux Mint!
Flatpak allows installing recent versions of important Apps.
Flatpak is well integrated in LM via the Software Manager. User can use the Software manger to install flatpak packages and even automatic updates are supported by LM.

However, the flatpak package shipped in LM CE (provided by Ubuntu) is severely outdated.
Currently, Linux Mint 22.3 ships flatpak 1.14.6-1ubuntu0.1

Ubuntu claims, that the last update to this package was in September 2024:
https://changelogs.ubuntu.com/changelogs/pool/universe/f/flatpak/flatpak_1.14.6-1ubuntu0.1/changelog

Since September 2024, flatpak had an impressive series of releases, fixing many security issues (closed CVEs) as can be seen here:
https://github.com/flatpak/flatpak/releases

However, since Ubuntu decided to no support flatpak as one of their core packages, none of the security fixes have been backported to the flatpak packages in use (in LM).

As of now, there are many security updates for flatpak, missing in LM CE.

It would be great if Linux Mint CE could:

• upgrade flatpak to a recent version for the releases of LM that are currently supported - in order to fix security issues
• check if flatpak can be maintained as part of the core packages of LM in the future, with backports or regular updates to stable releases.

Additional Information:
There is a PPA with stable, builds of flatpak, for all LTS branches of Ubuntu:
https://launchpad.net/~flatpak/+archive/ubuntu/stable

The Maintainer of the PPA writes: "This PPA is provided as a convenience for Ubuntu users, with no guarantee of support." It seems like this PPA is maintained directly by flatpak developers (to be verified)