Sure, the Linux ecosystem has not prioritized binary compatibility as much, so doing so has been harder, people culturally expected "use existing libraries" more than "just bundle everything", but as you note that attitude has shifted to and it always was possible.
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.
They all have sophisticated systems in place specifically to support third party software distribution that works (and is relatively safe):
• Windows has the app store, MSI, and MSIX (which allows efficient installs and updates from arbitrary web servers). MSIX is a package manager, by the way. It also has API support for writing AV scanners, managing software deployments across managed networks and so on.
• macOS has .dmgs, notarization, Gatekeeper
• Android has support for installing APKs from the web with a package identity system that lets anyone self-sign their software.
Above all they consider installing apps that aren't controlled by the vendors to be a core feature, so they work hard to provide binary compatibility, bug workarounds, multi-year deprecation cycles, anti-malware scanners and more, all for the benefit of developers who develop their apps independently of the vendors.
Linux can be reconfigured with additional repositories, technically, but that feature was originally designed for reducing bandwidth usage with mirrors. It wasn't meant to allow third parties to distribute software on their own schedule, which is why these third party repositories are invariably locked to a specific version of a specific distribution. Developers who complain about this are just told every version of every Linux distribution is a unique OS, and that they should open source their apps to let distributors centrally take ownership of their work.
It's changing a bit now with Flatpak. But for the bulk of Linux's history, that was the gig: no supported way to distribute your apps, and third party repositories would come with health warnings from your OS vendor. Not a supported way to use the OS. If it breaks you keep the pieces.
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.
So the Linux community doesn't get to cry freedom and decentralization now, IMHO. The time to do that was 25 years ago when Debian was being praised for having big repositories. Some of us actually did point out how centralized and authoritarian that approach was, I even built a system for distributing apps in binary form to all distros (with hacks and shims for binary compatibility), and that projects attracted some volunteers, but we got pilloried for not "getting" UNIX. One Debian developer even called us monkeys.
The users got tired of this and bypassed them with Docker, a much more decentralized system in which anyone can publish images without binary compatibility problems, and using them isn't tied to your OS version or OS vendor policies. But Docker is also centralized around Docker Hub, and Docker Inc do ban images and developers when malware is found:
https://jfrog.com/blog/attacks-on-docker-with-millions-of-ma...
Not so different to what the app stores do.
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.