Fallback for OAuth/OpenID Connect

I'm having a look to the authentication module OAuth/OpenID Connect (rolebased), having Azure AD as IdentityProvider.

It works so far for the WebDesigner Portal.

I'm just wondering if there is any fallback option. When I configure OAuth as primary authenticator it seems that the secondary authenticator isn't applicable at all.
Isn't it possible to configure an alternative authentication (i.e. on prem AD, or Person) in case of an outage of AAD?

We are running 8.2.1 at the moment.