There are two modules for this functionality: https://appstore.home.mendix.com/link/app/2948/Mendix/Google-Authenticator-Connector
Or https://appstore.home.mendix.com/link/app/105945/Finaps/2-Factor-Authentication-Module
I use the first one but are not yet on Mx8 with my apps.
Regards
Ronald
Integrate with an SMS provider and send your OTP using that service? Alternatively, Mendix has a Google Authenticator Connector in the appstore.