I wrote something about software distribution, incl. Flatpaks.
@clacke I don't see how Flatpak helps with that situation at all. The problem isn't that the user's system needs to have two versions of a library installed at the same time. The problem is that LibreOffice needs to be have source changes to work with the new library version. Until those are done, it's not possible to even build a new Flatpak version with the new library version.