Flatpak is more of a set of tools and framework. I wouldn't consider it as a store but a distribution system. Flathub is a repository, Fedora has its own repository and anybody can creates its own repo (I wouldn't call it store as there is no concept of monetisation).

I wouldn't consider flatpak as a gatekeeper as there is no "team" going through some arbitrary process to allow/disallow an app.

I also disagree with the fact that macos and windows did the right thing, what I found in my experience managing laptops in a company that is roughly 1/3 windows, 1/3 linux, 1/3 macos is that: - What windows is teaching users is to download random stuff and bypass the warning screens if something is not signed. Unless there is a company policy and a third party software to update what is installed, by default things installed are a mix of up to date and not update to date software. - Macos user do not install operating system and software updates unless a third party software is installed and force them too - Linux users have things up to date, only distribution version updates (e.g. fedora 41 to fedora 42) are inconsistent.

So my take is that, even if things on not perfect with flatpak, rpm/dnf, fwupdmgr and package manager, this is much better than having to pay for third party tools in macos and windows because of the lack of a good way to distribute and maintain apps at the operating system level.

Only fedora can put stuff in their flatpak repository presumably. That makes them a gatekeeper. Why is a repository needed? If it was the same, Mozilla would be able to put a flatpak file for Firefox on their website and it would be the preferred way to install Firefox.

Of course everybody (including Mozilla) can create their own repository and then you can install from any repository you like. But how is that different than just downloading whatever and installing that? And that's more of a hypothetical. Mozilla doesn't do that and doing such things is not common.

What Apple and MS enforce via signatures is that what you install and run was produced by somebody with a valid certificate that passed their screening.

The problem flatpak hasn't solved is that the likes of Mozilla still have no good way to distribute the most recent version of their application to all Linux users. So they put a tar ball on their website instead.