Gregory's Server> And the same for flatpaks, really. It is, right now, the only way you can distribute a piece of software for Linux and expect it to work anywhere.
This just isn't true. Firefox isn't distributed as a flatpak, but the version from Mozilla runs everywhere. We package Ardour for every version of Linux except nixOS (because they clobber LD_LIBRARY_PATH).
And flatpaks present nasty issues when used with software that can dynamically load 3rd party dlls.