My two cents: Keycloak's UI is pretty self explanatory if you understand OIDC (oauth2 + jwt + specific JWT claims) and, if you have to use it (my condolences, though it's also just interesting to see how crazy specs can get), SAML. I'd strongly suggest reading up on the OpenID Connect spec, including the oauth2 spec, and this will serve you very well in your authn/z journey.
That said, keycloak also does have a great docs site.
That said, keycloak also does have a great docs site.