Keycloak Kerberos prevent login dialog

I'm using keycloak to manage authentication of a java-based web-application.
I configured a Kerberos User Federation which is working fine within the internal network.
Accessing the web-application from outside the network I get the following login dialog instead of being forwarded to the keycloak login form.
Interesting the forwarding works with Firefox, but not Edge, Chrome, IE.

How can I prevent the login-dialog and forward directly to the keycloak-login-form?

EDIT: For example would it be possible to create a second authentication flow (with kerberos disabled) and pass it as parameter in the URL?

The Authentication Flow:

• Kerberos - ALTERNATIVE
• Forms - ALTERNATIVE

What I figured out, the browser-login-dialog is not shown and the flow is forwarded to the keycloak-login-page if the following settings are made.

• web-application URL is added to the "Trusted Sites" (either through IE settings or GPO)
  EN: Computer Configuration\Administrative Templates\Windows Components\Internet Explorer\Internet Control Panel\Security Page\Site to Zone Assignment List
  DE: Computerkonfiguration\Administrative Vorlagen\Windows-Komponenten\Internet Explorer\Internetsystemsteuerung\Sicherheitsseite\Liste der Site zu Zonenzuweisungen

• the following GPO setting is made
  EN: Computer Configuration\Administrative Templates\Windows Components\Internet Explorer\Internet Control Panel\Security Page\Trusted Sites Zone
  Logon options: Automatic logon with current user name and password
  DE: Computerkonfiguration\Administrative Vorlagen\Windows-Komponenten\Internet Explorer\Internetsystemsteuerung\Sicherheitsseite\Zone vertrauenswürdiger Sites Anmeldungsoptionen: Automatische Anmeldung mit aktuellem Benutzername und Kennwort