Starting from September 1st 2023, CERN upgraded their SSO to a standard OpenID Connect based solution. As a result, the previously builtin CERN provider is no longer needed and has been removed. Instead, use the regular OpenID Connect configuration:

    "openid_connect": {
        "APPS": [
                "provider_id": "cern",
                "name": "CERN",
                "client_id": "<insert-id>",
                "secret": "<insert-secret>",
                "settings": {
                    "server_url": "",
App registration (get your key and secret here)

CERN OAuth2 Documentation