Using keycloak as gitlab-ci service

I am trying to run my integration tests in gitlab-ci versus a keycloak instance started via a service. gitlab-ci yaml configuration can be found over here:

  - docker:dind
  - name: mongo:latest
    alias: mongodb
  - name: jboss/keycloak:10.0.1
    alias: sso
    command: ["-b", ""]

Now I can’t connect to this instance.
I added some curl commands to validate the connection, but there I see something strange happening:

going to http://sso:8080 gives the following (keycloak) response

 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
     <meta http-equiv="refresh" content="0; url=/auth/" />
     <meta name="robots" content="noindex, nofollow">
     <script type="text/javascript">
         window.location.href = "/auth/"
     If you are not redirected automatically, follow this <a href='/auth'>link</a>.

which means that keycloak is up and running.
Then, connecting to http://sso:8080/auth gives a 404…

I would expect that this was due to not binding to, but I did this in the service configuration.

Anyone having a clue of what I did do wrong?