librekittyBlockAds is a great FOSS android app (available on f-droid/Izzy)
it uses local filters to block ads, trackers + analytics, and more 🚱
i was surprised just how much stuff was being sent that BlockAds saved me from, even from some other FOSS apps 🙀
it's a must-install, i also reccomend setting it as an "always on" vpn in android settings too