OAuth2 based SSO

We are providing a platform similar to a marketplace to our customers. In the future, we want to offer our products from AppXite in our platform as well.The usecase will be: We export products from AppXite, display these products in our maketplace and send the customer to AppXite if he wants to subscribe to a service.
With the current possibilities the customer would have to register himself on our AppXite platform again. We want to avoid that since we already have a OAuth2 based SSO in all of our platforms besides AppXite.
As far as I’ve read, we are only able to authenticate the customer through the AAD at the moment. It would be great if there was an OAuth2 approach as well.