Support for adyen_hpp payment method is built in as of 1.2.052 of OneStepCheckout 

If you still using out of date OneStepCheckout  or Adyen extension then the path to solve the incompatibilities is to upgrade both tho latest versions. 

Deprecated:

This patch is meant for Adyen_Payment extension extension compatibility:

Main conflicting issue is that "adyen_hpp" method inside this extension does not follow Magento 2 API for frontend payment methods and implements a set of "virtual" or "fake" payment method listings identified by brand_code instead of method_code and is missing some expected methods for Payment method objects

Solution is to patch following OneStepCheckout file:

[OneStepCheckout installation path]/view/frontend/web/js/payment.js and replace method "selectMethod"

with following method:

Replaced method adds conditions needed to detect payment methods by brand_code and also implement at least one expected method to its options.