Exactly this. OIDC and SAML integrations with customers IdP's. Map identity metadata from the customer into our realm so they can provide data in any way they want and we map it down to our standard which allows our applications to stay clean when using this metadata for business logic.
We have also added an event plugin to keycloak to push login events to a queue for other services to consume.
We also offer local keycloak identities in case a customer does not or can not provide their own identities, and have added haveibeenpwnd logic to check password strength/reuse for these local keycloak identities.
We have been using it for 6-7 years now. Have been able to run very stable and integrated a lot of external IdP's to offer proper SSO on mulitple of our software stacks. Added a lot of other open source pieces of software we run for our backoffice needs (hashi vault, adminbro, etc.). So far very happy with it. Running in clustered mode without issues and as such little issues with the startup times. It probably helps that we have a solid background in Java based development and deployment and are less worried about the amount of memory it uses for the full suite.
We have also added an event plugin to keycloak to push login events to a queue for other services to consume.
We also offer local keycloak identities in case a customer does not or can not provide their own identities, and have added haveibeenpwnd logic to check password strength/reuse for these local keycloak identities.