Small tangential rant:

Ever since an iOS update last year Firefox (well, the Firefox-branded Safari browser for iOS) doesn't block ads for me anymore. I really noticed that my mobile data usage spiked since then. There's all these adblocker apps in the app store, but they seem rather scummy and the few I've tried don't appear to be working with Firefox anyways.

It's ridiculous considering Apple is declaring itself the champion of privacy. I might really have to rethink if I get another iphone next time I'm buying a smart phone. Not that Android isn't equally terrible for different reasons..

Uh, what? Content Blockers on iOS aren't scummy, they can't track you because all they do is provide filter lists to the OS, which then runs them against your browser traffic. They work just fine in Firefox. Firefox Focus provides its tracking protection list as a Safari Content Blocker, which is nice. Other than that, I use AdGuard because it's free and lets you choose which filter lists to use.

You have to enable content blockers in Settings → Safari → Content Blockers. Just downloading the app without following the instructions is not enough.

>AdGuard

I'm sorry, but a closed-source ad blocker offered by a for-profit company and offering a pro version seems scummy to me.

I'm sorry, but that's nonsense. AdGuard doesn't have any scummy stuff like "acceptable ads", they make money by providing a fully functional free ad-blocker and selling a version that has more features. That's as un-scummy as it gets. (I have no relation to them. I use the free version. It does everything I want.)

By the way, you can get the source code at https://github.com/AdguardTeam/AdguardForiOS.

There's also a list of open-source content blockers at https://old.reddit.com/comments/btlwda/, some of them are non-commercial.

Welp, I tried AdGuard again and it still doesn't work with Firefox. Safari blocks ads just fine but Firefox still shows them.

iOS content blockers only work with Safari.