OpenProject v9.03 on Debian 9 works great using OpenID with Keycloak Server. After upgrade to OpenProject 10.0 OpenID doesn't work anymore with the configuration below.

Instead of redirecting a user without valid ticket to https://auth.mserver.org/auth/realms/master/protocol/openid-connect/auth?client_id=OpenProjectMartin&nonce=762d9653255d825d59f8a9cd66e1953b&redirect_uri=https%3A%2F%2Fopenproject.heiliger-martin-kaiserslautern.de%2Fauth%2Fkeycloak%2Fcallback&response_type=code&scope=openid+email+profile&state=8f713708462dcdde48b8b6c471297cea

user is directed to https://openproject.hserver.de/auth/keycloak with error message: Fehler: Datei nicht gefunden      Beim Verbinden mit openproject.hserver.de trat ein Fehler auf.

The working configuration (till v. 9.0.3) in file /opt/openproject/config/configuration.yml below default:

 openid_connect:

   keycloak:

     sso: true

     host: "auth.mserver.org"

     identifier: "OpenProjectMartin"

     secret: "e333-333-333-33333-3333-3333b"

     icon: "openid_connect/auth_provider-google.png"

     display_name: "KeyCloak Authorisation"

     authorization_endpoint: "https://auth.mserver.org/auth/realms/master/protocol/openid-connect/auth"

     token_endpoint: 'https://auth.mserver.org/auth/realms/master/protocol/openid-connect/token'

     userinfo_endpoint: 'https://auth.mserver.org/auth/realms/master/protocol/openid-connect/userinfo'

     end_session_endpoint: 'https://auth.mserver.org/auth/realms/master/protocol/openid-connect/logout'

     check_session_iframe: 'https://auth.mserver.org/auth/realms/master/protocol/openid-connect/login-status-iframe.html'

     issuer: 'https://openproject.hserver.de/login'

     discovery: false

 disable_password_login: true

 omniauth_direct_login_provider: keycloak

Regards

Andreas