[keycloak-user] Authentication with Kerberos and login screen fallback

Hello guys, I have an web application where I'd like to use Keycloak for authentication. If possible the user should login via Kerberos. If not use login screen. On my computer I have a valid Kerberos ticket and the login works fine. If I try to login for example from another device I always get the error-code 401. I expected to get the login screen instead. If I configure the trusted-uris on these device the login screen appears.  I successfully configured an LDAP User Federation provider with Kerberos integration. I used this instructions (https://www.keycloak.org/docs/2.5/server_admin/topics/authentication/kerb...) to create the authentication flows. Is it possible to use Kerberos authentication from known devices and use the login screen from unknown devices where I can't configure trusted-uris? One example could be my mobile phone where I'm not able to configure something. Thanks in advance.