Other than the usual settings such as turning off location services, not installing most (or all?) third party apps, is there anyway to prevent data leakage?
I'm most interested in ad-networks, data brokers, etc and keeping as much from them as possible. Also to an extent possible, limiting as much to Apple.
What are some tips to make this work?
Front page of HN today https://news.ycombinator.com/item?id=25078034
I've read that Google and Apple backdoor their own processes so they can't be disabled. Google runs sensorvault, and shares that information.
As far as I can tell, Apple mainly wants to keep you in their garden, buying expensive hardware, while Google wants to sell you over and over.
Probably your best bet is to look toward a linux based phone such as Purism (expensive), Pinephone (beta quality) or make your own (not that practical).
It would probably be useful to know what you want to be able to do with your smart phone to give you better advice.
I have a friend who's insisting not to do that and his life is miserable. Too many of the Apple basic features/services today require 2FA. If that's a deal breaker, I'd highly recommend to not go for an iphone.