On AOSP they aren’t tracked it’s a De-Googled OS it has no Google Service Framework or Google related apps to track you, you’d use the F-Droid marketplace for none tracking apps to install on it if needed.

Expense I can understand, but something of a natively compatible format for installing the Android Open Source Project (AOSP) sounds fine to use as a kind of capable dumb phone if you like and by capable I meam it can be used as both a smart phone or dumb phone with the use of a launcher being installed for the dumbing down, say some text based or other simplistic launcher available via F-Droid.

Cost is not to viscious for Android phones of just ok spec like an old mid range octa core running Android 11 or Android 12 with say 64gb storage to 128gb storage but 32gb is fine even less really but you begin dropojng soc performance fast going to 32gb storage devices really but in those 64-128gb eras of hardware ranges are pretty cheap now for second hand ones with warranties sometimes to. AOSP is lighter on resources trick also is enable developer options and turn off

1. Window Animation Scale

2. Transition Animation Scale

3. Animator Duration Scale

This makes a device fly scrolling and opening and tapping things to open them because the you aren’t waiting for transitions to take place for the UI that often has a momentary pause or animated effect to look cool but this might look cool but it slows the waiting time to ooem things right down, I always disable that on all phones or other Android devices that run Android on initial setup.

Or if you want true dumb phones a 4g doro lol

For iphone’s I just found this it’s pretty interesting turning it into a light phone by a launcher.

https://www.youtube.com/watch?v=10iUIoVBRI8&t=47