The only way is using the API connector and Stripe’s “Managed accounts” feature.
But don’t forget, in iOS applications you aren’t allowed to collect user’s credit card information - you are only allowed to use app-store payments, you are only allowed to collect credit card in apps if your users are receiving a physical product.
If you are selling in-app products or features in your app then Apple will not let you onto their store, even if they don’t catch it they’ll ban you eventually.
If you were planning on selling app features or online products then you’ll have to wait as Bubble does not yet supports in-app payments.
That said, I’m also waiting for that integration, I built an app without doing my research about in-app payments - and this app heavily relies on that feature.
Hopefully it’ll come this year or the next.
Maybe @josh could give us an update on that.