going further away from the android/AOSP-derivatives: another solution is Linux distributions on smartphones:
- I personally daily drive #SailfishOS for more than a decade (commercially supported versions of SFOS even have "Android App Support" running inside a container for "that one app" with no native linux port you can't get without)
- I've heard positive things about #postmarketOS and #UbuntuTouch (but don't have personal experience)