According to the tracking scanner Exodus (can be found on F-Droid), which keeps an updated database on trackers and runs your installed app against its register, you can track what apps are tracking you and clues of how. Saw that Boost is tracking me and uninstalled it and went straight to Jerboa. Jerboa is pretty similar to good ole’ RedditIsFun-app and easy to use, so I am personally recommending it.
From F-Droid:
Exodus (Exodus show you trackers and permissions in apps installed on your device.) https://f-droid.org/packages/org.eu.exodus_privacy.exodusprivacy/
Ads generally come with tracking, since the advertiser wants to know their ad was seen / effective. Some ad systems might be better than others, but I don’t have experience there
I know Mozilla is working on ‘Privacy respecting ads’, which was also controversial: https://www.mozilla.org/en-US/foundation/annualreport/2024/article/a-privacy-first-solution-that-meets-advertisers-needs/