Yeah, that’s not happening, other than at the low end with ChromeOS. We’ve seen it in the 1990s, and we’ve seen it again in mobile OSes in the 2010s: a third platform cannot thrive.
Sure, or more realistically, there is often only 1 that completely dominates. Windows completely dominates the desktop, with macOS a minor player. Linux dominates internet servers, and completely and utterly dominates super computers. Android for mobile, although iOS is significant, especially in richer countries.
But we've also seen over and over again that the dominant platform can get complacent and get knocked off the shelf. Off the top of my head, I'm thinking IBM, Blackberry, and Nokia for a start.
As a Mac and iPhone user, I love them, and hate them. I love the user friendliness. And I love the power user capabilities of macOS with it being built on *nix underneath, and having access to the *nix terminal command line. But I find it constantly frustrating how each successive release of macOS
removes some of the power features. I don't know if it is meant to "protect" the non-power users from themselves, or if it's pure control freakiness, or if it's simply laziness to have to maintain such features, or if those features are being removed into a paid-for product. Whatever it is, it's exasperating. And iOS, sheesh, the walled garden is super annoying. As is the complete lock down and removal of access to the most basic of the underlying *nix features. For example, even a decent file system FFS. And it mostly just gets progressively worse, year after year.
And what are the alternatives. Windows, not thanks. Linux, sure a decent power-user option, but clunky and lacking in many ways. Android, gah, I tried it, but it's mess.
All it will take, is some nerdy billionaire, or his nerdy kid, who has similar thoughts, and puts together a dream team to create an alternative, with all the great things about the Apple hardware-OS combination, but without the locked down, control freak, profit greedy, annoyances. Maybe throw in genuine care about the environment, rather than empty virtue signalling, with genuine repairability and upgradeability. And boom, Apple suddenly has a big problem, and has to start cutting its profit margins, and killing its most greedy practices to simply survive.