If your problem is that the form fields are not appearing on the screen, leaving you with just a white box, then the cause of this is that it is blocked by security (you can see an error in the logs in Xcode when you try to mount the element on the page). The Stripe elements renders inside an iframe. You need to add to your config.xml:
It’s funny, I’m using Stripe.js without elements, I just use the js api (createToken()) and it did nothing on ios but worked on android, so I tried allow-navigation without much faith and it actually solved my problem.