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.
The main issue being solved here is that security relies heavily on those actors like Google and Apple. Banks, companies etc. have high security requirements (rightly so) and basically need to tick boxes. So if the only way to obtain, say, MFA, is through something only Goole/Apple provides, they will require Google or Apple devices.
If we had reasonable standards alternatives can become a reality.