It blocks trackers in other apps, not just in its own browser.

It does this by acting as a VPN last I checked, so it wasn't useful in my case because it couldn't run at the same time as my other VPN.

A handy alternative, is to temporarily utilize the app over a week or two to see what's making requests and then go into app permissions on that app and prevent it from using mobile data in the background and running in the background.

Is there a good reason to ever allow any app to do these things?

Yes and yes: I use syncthing, and I just want it to make the changes in the background. My best case scenario is never opening the Syncthing app again, because it's quietly doing it's thing in the background, sometimes on data.

Otherwise, my girlfriend, parents, and likely 90% of the people you know all use photo backup. Whether it's iCloud, Google Photos, or a NAS, we all want the option to use mobile data, and likely want it to simply run in the background.

I use a similar one called TrackerControl (from fdroid) it is just incredible the number of trackers inside a single app. Some have over a dozen, this is getting out of hand.

I'd never heard of this and went to go try it. I very disappointed to find it required me to turn off my existing VPN and wanted me to disable DoH :(

It's probably using the VPN mechanism to grab traffic for inspection and can't do what it does without that.

If it can inspect the traffic, why would it demand I turn off DoH? I could understand one or the other, but both?

because you can't do dns level blocking with doh because of https.