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.