> And, note, back when I was a Linux user, distro vendors and evangelists justified that situation by security. They said we don't want people distributing software outside of our repositories because that's how Windows users get viruses, so we deliberately won't make it any easier.
Never heard that argument, ever. `apt-get` literally allows you to add whatever repositories you want. You're conflating two completely separate worlds. The first is the world of Linux that pretty much invented the idea of a software repository for an operating system. This was invented because Linux has the notion of "distros", and the trick there is to provide a set of packages that all work together in that distro. That's the purpose of curating packages in the repos (along with Free Software licensing, in the case of distros like Debian). But this system was always federated, where users were empowered to add any additional software repositories they needed. F-Droid on Android copies the exact same architecture, allowing the user to add endpoints of servers they want to pull software from.
The second is a system of control built by Google and Apple. It has nothing in common with the Linux system, but rather was designed to vend proprietary software that extracted money from users, for the purpose of lining Google and Apple's pockets. When Tim Cook testified about app store fees and the judge queried him about why they were so high, he said "To lower those fees would be to give up the full return on our App Store investment." Basically: we're charging this much because we can.
Conflating these two systems and the reasons for their design would be very misleading.
> It's fair to say that the only OS vendors who have ever taken decentralized and free app distribution seriously are Apple, MS and Google. The open source world went all-in on the centralized store model from the start and never looked back.
It is not even remotely fair to say this. In fact, it's so misleading it feels malicious. The only operating system on the planet that offers user-supplied software repositories that work with the built-in package management system is Linux. Full stop. And Linux doesn't even only have one of these systems, it has several. Flatpak, Debian repos, Ubuntu repos, Arch's AUR, Slackware's third party repos, etc. And users don't have to "work around" the system to use any of this - simply adding new URLs works great, and it's always been this way.
https://wiki.archlinux.org/title/Unofficial_user_repositorie...
https://documentation.ubuntu.com/server/explanation/software...
In short, Windows and MacOS and Android have never taken third party software distribution seriously in the least, and have done nothing to support it. Linux has built-in support for third-party repositories, and has for decades.