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.
Years ago I loved tinkering with the devices but then I wasn't able to use my bank and it was getting more and more annoying so at one point I just stopped...
The biggest problem are: 1) lack of drivers (so creating custom roms/OS for the devices is problematic), 2) locked bootloaders and 3) many apps requiring PlayServices and other stuff (mostly banks).
There is postmarketOS, it looks awesome but - device support is very lacking and there is no way to have bank and PopularApps (whatsapp/instagram/etc) running on it so it's popularity is microscopic…
Maybe another European Citizen Initiative to force makers to provide those things (bootloader and drivers)?