For example, RCS only works with Google messenger and there's no sign of that expanding (unless your Samsung). Even Visual Voicemail which should/is an open standard has a lot of carrier specific code (I think it can still be extracted from the Google Phone app but I'm not sure on the license).
NFC payments (tap2pay) seem to be impossible outside the few blessed implementations and even running those is a cat & mouse game with SafetyNet (now called Play Integrity).
Android is still the most open source mobile OS (that's functional and has real security; mobile Linux doesn't count). But IMO it better remember why people pick it over iOS.
I'm still optimistic, if open standards for the basic functionality is going to survive; it will be on Android.
- Sent from my Google Fold running GrapheneOS.