The current default SignInPage component implementation in the new frontend system app is hard coded to only reference the guest authentication provider. One immediate option is to add an override using the existing extension point in our own app-next and continue using our existing sign-in page by copying it over. This also seems to correlate with the guidance given in the migration guide under this section (search for SignInPage).

Ideally whatever solution we go with should avoid adding substantial implementation to the app-next package if possible, for example bringing over the existing SignInPage code could be a bit against the grain of what we would like to achieve with RHDHPLAN-933