For normal apps, one can add the "product" Facebook Login.

For apps that are categorized as "business", Facebook has this preferred auth mechanism called Facebook Login for Business (ref: https://developers.facebook.com/docs/development/create-an-app/other-app-types#step-3--select-an-app-type)

However, the latter has more requirements than the former and doesn't seem wo work in Firebase Auth

Users have to create a Login Configuration (which gives you a configuration id)
When using the SDK, pass the configuration id:
Documentation says:
When invoking the login dialog and setting the redirect URL, include your configuration ID as an optional parameter (although scope can still be included, we recommend that you do not use it).