For example, does your HackerNews app need to talk to Google? Probably not, so that gets blocked by default. Does your Newpipe/YouTube app? Yes, so you should unblock that from talking to Google. The Spotify app also tries to talk to like 9 different tracking domains, but only one category is actually required to fully use the app. Screenshot: https://dro.pm/n.png (Current version doesn't yet allow toggling per-domain in an attempt to make it easier/more manageable; but iirc allowing that is a planned change.)
The app is under active development and the dev seems to listen to feature requests, so if you have any... :). One downside is that it doesn't work alongside other VPN apps because it pretends to be a VPN. If anyone has a good idea how to solve that, the dev asked for ideas if I remember correctly.
I already blacklisted advertising domains in /etc/hosts and disabled things like broadcast listeners so certain apps don't receive the OnBoot/OnAppInstalled/etc. events to limit what they notice and can do, but with TC I feel like my privacy on Android got a substantial boost. Spotify was the last app I use with Facebook integration and I was wondering what to do about it, but I think that is not an issue anymore now.
[1] https://f-droid.org/en/packages/net.kollnig.missioncontrol.f...
I don't currently use an iPhone (contemplating jumping ship as well), but my understanding is you can get similar functionality on there using AdGuard.
There is also Pinephone with pure GNU/Linux and killswitches.