Here's what puzzles me. I have looked into Stripe, and just browsed the Adyen webpage. Both of those services seem to require you to maintain your own "active" server that can run server side code. PayPal seems to be unique in being able to take payments from a passive web page, because the customer conducts their transaction at PP's website. This is why I continue to use PP for my tiny little business (without eBay)…
There's a shared secret you can use to verify the payment when they callback to you after payment, and their HPP is skinnable.
[1] https://docs.adyen.com/developers/api-reference/hosted-payme...