As we use the auth_external module to use our own authentication procedure, we have a working solution. But is not so nice.
I have unregistered the normal member authentication process with

Authenticator::unregister('MemberAuthenticator');
Authenticator::register_authenticator('ExternalAuthenticator');

both in mysite/_config.php and saphhire/_config.php

But when I use the login form ($LoginForm) in template files (layout/myauth.ss), I still get the layout of the normal login form with Email and Password, what I cannot use.
I tried to use $ExternalLoginForm, but this returns empty.

Anybody has an idea about this?

Walter

I put only
Authenticator::unregister('MemberAuthenticator');
in auth_external/_config.php

It is all documented here:
http://doc.silverstripe.org/doku.php?id=modules:external-authentication&s=auth external

I only see the External Authentication Form

I have the same problem that WalterW.

Hi!
I know it's a bit late but I found a solution to the problem.
You have to override the function LoginForm in the page controller to get $LoginForm point to external authenticator instead of member authenticator:

class Page_Controller extends ContentController {
        //...
	public function LoginForm() {
		return ExternalAuthenticator::get_login_form($this);
	}
}

With this you can use $LoginForm to display the external authenticator form.