I found some tips:
Authenticating your users via Microsoft using Firebase
B4J Tutorial [B4x]Google Authenticator OTP (others will do, too) complete example with code
Android Code Snippet [B4x] Use OTP in your apps (php code also included)
B4R Tutorial ESP32: OTP/2FA example
There is also this...
This example generates a OTP/2FA ("One Time Password") as you know it when you login to a website and you get a 6 digit code via sms. It changes every 30 seconds.
How it works:
- as it is time based, you need a internet connection. Please add your wifi/router credentials
- time is retrieved...