Flask-Admin provides the examples of authentication with Flask-Login and Flask-Security. Here is an example how to authenticate using Microsoft oAuth.

Create an application in Microsoft Application Registration Portal.

The connection to Microsoft Graph with Flask-OAuthlib described well in this tutorial.

One detail it’s missing - how to refresh the access token, because it expires in an hour. In Flask-OAuthlib there is no method for this but it can be done easily with a POST request.