Hi @oscarlj
I hope you’re well today!
Currently Forminator supports only Stripe and PayPal and there’s no direct API/interface specifically for other payment solutions.
To integrate any other payment directly to Forminator forms, it would require complex custom code based on general Forminator API and hooks.
This API could be used to too interact with forms and together with built-in action/filter hooks it would be possible to intercept form data and stop (error) or execute submission based on some custom code (which could interact with any external payment API).
It is beyond the scope of this support, I’m afraid, but if you feel like coding it yourself – you’ll find Forminator API docs here:
https://wpmudev.com/docs/api-plugin-development/forminator-api-docs/
Kind regards,
Adam