Does anyone have the answer from Cardinal?
I gave up on Cardinal. Even their website for signing up seemed ancient. Also the fact that they not supporting NopCommerce yet they said they may do in furmture but I'm not holding my breath.
I've been speaking to PayPal direct who have been helping to integrate with PSD2. The only options I have are PayPal hosted version (using PayPal Standard plugin using IPN and PDT token). This option redirects user to PayPal and allowing guest option and making credit card payment. Other option is using I frame (I'm not fan of this) The only alternative to PayPal Direct is to use Baintree but I currently I don't really want to sign up to another payment provider. So I'm sticking with PayPal standard for bow until a better alternative comes along or I can get some integration guideline from PayPal to get PayPal direct working with PSD2. So my customers should still be able to make credit card payments without PayPal account.