Yo Dawg, I Heard You Liked App Stores
Two major Apple competitors, Google and Microsoft, now support alternate app installation options on their platforms, something that could potentially sway regulators working on antitrust legislation in the United States and other countries.
When I heard the original part of the Windows 11 announcement, I got the sense that the Microsoft Store would become either a store "platform", where other people could host Microsoft Store-shaped objects or a browser, through which other stores could be federated. Making the separate stores available for download through their store itself (which is mostly what it all comes down to) is a reasonable way to cut this Gordian knot.
But here's the thing. Alternative Android stores, alternative Windows stores — they already exist. They have existed for years, the technical platform has existed for years, all issues have been ironed out or known for years, and the major tide has been closing an open system (for Android, "anyone can do anything", for Windows, "Microsoft can't build a regular application cooler than you can" (literally)).
For Apple, the starting point is the complete opposite. A closed system, including a secure (in theory) sandbox architecture, with isolation of resources, deep layering in the system from bootloading upwards, and with "entitlements" and a set of permissions to unlock or manage who gets access to what. And, at the top, an App Store to download new app bundles to the device, and to set ongoing organizational policy about who gets access to what.
A third party app store (or package manager like Cydia) which wants to use this system has to have the routes to playing the App Store piece cleared to it, and for all the dozens of policies for which apps get to do what, in each case where Apple is listed as the arbiter, there will need to be a decision to delegate it or not. For instance, a third party app store could have a more laissez-faire approach to who gets to write a Network extension (VPN) or primary web browser.
There's also the gooey technical middle ground - for example, if you want to allow multiple web rendering engines, is there also then a need to make apps that can themselves provide frameworks to other apps? Personally, I think apps being able to work together and provide extensions, opt-in mutual integration points in an XPC-like way or export/import data in a way that uses the ask-for-get-granted-permission system to its advantage is long overdue and would leapfrog the current URL/Shortcuts-based workarounds.
But that underlines the work involved - even if Apple was ordered by the Andorran consumer protection government agency to provide a shrinkwrap App Store that other people could instantiate, those other people could not extend the underlying system, could not build out extensions, could not provide new permissions or entitlements. On Windows and Android, that's not an issue because it's not required (and for permissions and entitlements on Android, the OS itself can be forked, or maybe there is a lighter-weight way for the vendor to maintain custom permissions that I am just unaware of). On macOS, for all the unease about clamping down, there are already other app stores like Steam and Setapp that continue to work. But on iOS, there are basically more pieces missing than are present.
Right now, Apple seems to be coasting by on the pious hope that the entities that are able to order them to change their business will continue to be amenable to lobbying that defines their interpretation of the current state of affairs as the correct one, or failing that, that they will have some level of understanding and therefore sympathy for the sweeping and foundational efforts that would have to be made to enable other app stores — I can guarantee that they won't.