I'm not sure if i missed it but you did mention physical keyboard;

Without this physical keyboard, you have phones like https://puri.sm/products/librem-5/#overview

Also there are plenty of non google service based android phones and alternatives.

You can also use Linux on most Android Phones as well.

A Pi Zero or a Pi in general is very very far away from what a Android based Phone does and can do. Alone for Security.

What is your thought why you would assume a lot of people could get beind this setup? I do like the project, its nice though but for me probably for different reasons then for you.