We have a client that uses SAML requests with the AssertionConsumerServiceIndex attribute. This index contains different values that lead to different service URLs. When we tried to use RHSSO as the IDP for this client, the SSO redirected the client to a single URL.

Keycloak as an IDP does not currently offer any options to configure AssertionConsumerServiceIndex.
This index contains different values that lead to different service URLs. This essentially allows the IDP to configure multiple ACS urls and then the samlresponse will be sent to the AssertionConsumerServiceURL from the SAML SP AuthnRequest.