Android shouldn't be considered Open Source anymore, since source code is published in batches and only part of the system is open, with more and more apps going behind the Google ecosystem itself.
Maybe it's time for a third large phone OS, whether it comes from China getting fed up with the US and Google's shenanigans (Huawei has HarmonyOS but it's not open) or some "GNU/Linux" touch version that has a serious ecosystem. Especially when more and more apps and services are "mobile-first" or "mobile-only" like banking.
That idea died for me long ago, I had used Android since 2009 till 2020. I gave up on the dream of a Linux phone. Ubuntu had a nice sleek Phone UI they were working on. The issue is if nobody builds the phones and no carrier cares, nobody will pick it up. You need to push yourself into the market.
Microsoft could fill this weird gap if they wanted to the key things would be they would have to truly open source the OS. I could see Amazon trying again, but they'd need to invest a lot as well. It's an uphill battle needing a serious flagship phone. Your other problem is most apps need to be migrated.
Until we have serious antitrust legislation against Google and Apple wielding their market power against any new entrants we are stuck with a duopoly.
At the very least, Google needs to lose Android, and probably YouTube as well.
Wishful thinking department unfortunately. Modern US capitalism wouldn't allow that to happen—and a large majority of users are so addicted to the electronic heroin provided (seemingly for free but not) by the likes of Big Tech—Google et al—to care let alone do anything about the problem.