A common question users ask is how to add a new payment processor – such as Adyen rather than Stripe or Paypal. It’s fairly easy to do this, here are brief instructions so you know which files to modify
To add a new payment method:
Http/Controllers/Account/BankAccountController.php - to create a new account.
Http/Controllers/CheckoutController.php - to confirm payment.
and the associated views.
resources/themes/default/listing/widgets/buy_widget.twig - to open the payment widget.
resources/themes/default/account/bank_account.twig – so users can add their bank details, account number etc.