Is the Authenticator SPI supported in RH-SSO ?

Hi,
i need to build a custom authentication flow to interact with esternal OTP product. I've seen from the documentation that Keycoak provides Authenticator SPI in order to do that, but RED HAT SSO documentation doesn't mention it. Does it mean that Redhat doesn't support that SPI? Is there an alternative way to build a custom authentication flow like that?
Thank you

Regards

Emidio Laterza