NMI Payment Gateway
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I own a CBD store and since it is "high risk" there are only a few providers for taking payments, and they all tend to use NMI.
Some snippets of info that might give you some hints as to what is needed to build a integration.
The bank is First Financial, who use NMI as their gateway. Docs: https://fdf.transactiongateway.com/merchants/resources/integration/integration_portal.php
Screenshot attached from the plugin I currently use - XL NMI gateway config page
And it looks like collect.js to tokenize the card info + the api is to send the tokenized card info thru the gateway. I'm guessing you need to store the token for subscriptions like Stripe.
Let me know if there is other info that would help.