How to cancel Apple Apps formerly purchased with monthly fees

What Apple apps have monthly fees? Should one only be if you are paying for Apple Music, Apple TV+, Apple News, iCloud storage.. or one of the Apple One plans that includes combinations of those.

You should find any active subscription listed in Settings > [your name] > Subscriptions

If it's not one of the items I mentioned above, it's not likely it's an 'Apple app'. All those apps that you find in the App Store, the vast majority of those are apps written by non-Apple developers

Those subscriptions should also be listed there.

Subscriptions and Billing - Official Apple Support

There is an Apple article that explains how to cancel subscriptions. Click on the following link: If you want to cancel a subscription from Apple - Apple Support