I use Spotify, FreeAgent, Toggl, Zoom, Pipedrive, Asana and Trello (plus Basecamp previously) on my iOS devices - and pay for all of those through the respective websites without any option to pay in the App Store.

(Edit: I know Spotify used to have an option for it but they dropped that and I never used it anyway)

It doesn’t force you, but if you don’t, you can’t even tell people how to subscribe. See Spotify, Kindle.

You can tell people how to subscribe outside the app.

But you just can't use Apple's own platform against them.

You can't link, at least, to an external website to buy

https://www.pcworld.com/article/229880/Apple_Backs_Off_In_Ap...

You can't even tell that such a thing exists. E.g., Audible only gives you an option to add to the wish list, and is mum about how to buy a book.

So in a way apple is forcing them.

Hm... The Amazon Prime app doesn't allow purchases in the app, you've got to purchase through Amazon and then you can watch them just fine.