Use Stripe for in-app purchases on the US App Store π΅

Trying to publish an iOS app that uses Stripe instead of native in-app purchases to the US App Store?
Now that Apple is allowing fee-free link-out on the US App Store, you can use third-party payment processors like Stripe to save up to 27% on in-app purchases.
There's surprisingly little documentation on getting this approved through Apple's review process, and even after reviewing their updated review guidelines.
And Apple's rejections aren't exactly explicit about how to get through app review with external payments:

So I'll share what I've learned after a few days of trial & error with Apple's review team:
- Your payment button needs to bump the user to their web browser app, not a web view inside of your app.
- Your paywall CTA needs to make it clear to the user that they will be redirected to a web page to complete their purchase, including an external link icon.

- Ensure your paywall is easily accessible to the App Store review team, and include instructions for accessing it in the Notes section of App Store Connect.
- Reminder: ensure you're only doing this on the US App Store. Other stores must use native in-app purchases.
That's all! I hope you get your app approved on the first go..