I tried to use the OTP two factor authentication in Keycloak. It is very easy to use and works fine with Google Authenticator. Because I normally use the Microsoft Authenticator, I tried it too. It is working, but not listed as a supported OTP Client (FreeOTP, Google Authenticator).
Is there a reason why it is not listed?
IMHO only the most known TOTP apps have been mentioned in the GUI. But TOTP si well known so it should works with any TOTP apps. I used it with Yubico authenticator, Duo Mobile.
BTW: Google and Microsoft have had (maybe it is still not fixed) vulnerability in their TOTP Android apps https://www.techradar.com/news/google-2fa-authentication-could-be-less-secure-than-thought
If you want to add more apps to your end users, you can edit it creating your own theme.