Don't you use Keycloak for SSO? The ports needed for that needs to be accessible so services can talk to it. If there's a dedicated port for management you can still use it with software like pangolin. Run the management service on only a local port and access using this software or wireguad.

I use authentik and as far as I know the management is on the same web port so I have to allow some paths to be accessible to the world.