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.
All that type of money went to llms, who is going to spend that on a phone os now? Not who should, but who actually would? They gave up on browsers, they gave up on mobile oses. There is a real risk that the next step is the US gov takes X% of google instead of enforcing antitrust in a year or two.
Linux phones will never take off because banking and media/drm apps, and by extension social media apps, will just boycott them and kill it off. The tone has been set, this comment applies to any major player trying to break into the mobile market moving forward.
This is honestly very bleak news.
I'm just name dropping from the perspective of a big org that could fund such a thing correctly, but they would need to start over IMHO.
I'm not sure of another big player who could invest billions into such an endeavour.