Richard Stallman was right. Buy a dumbphone, an actual one. Call's, SMS', nothing else.

Did you know that women's period was tracked by propietary smartphone apps?

There goes your freedom.

https://www.bbc.com/news/technology-61952794

You can still be location-tracked with a dumb phone. Yes, even if the phone has no GPS. Any communication with the network gives away your location to the "right" people.

it can, but it's significantly harder. With good enough opsec the info leaked through cell activity is practically negligible

Pocket Faradays cages (and metallic clothes) exist. In the end if you use as a landline phone substitute it's almost a hardware issue and software would be just testimonial there.