This one is from the top of my hat because currently the documentation is not visible in the appstore. If I remember correctly Mendix uses open ID. And in the appstore there is an older module that also uses open ID: https://appstore.home.mendix.com/link/app/1206/Flock-of-Birds/Social-Authentication
You might try that one to see if you can authenticate Mendix users.
Regards,
Ronald