IMHO the best option for a secure phone is pure Android without Google blobs. That is, AOSP on a Pixel phone. Plus an F-Droid userland.

If a Pixel is too expensive, you can always try to get an AOSP device-independent image on a new phone that supports Treble. For example, the super cheap Nokia 1 seems to work well [1].

[1] https://github.com/phhusson/treble_experimentations/wiki