Basic question

Is there a way for a browser to detect whether a user has been authenticated via SAML on a different site?

Background

My organization has a custom application that is a portal that uses an iframe to serve up reports stored on two different servers, Tableau and PowerBI. The Tableau and PowerBI servers use SAML authentication and require MFA. When the portal opens, it’s supposed to open a Tableau report on the home page. In the past, the Tableau authentication could take place in the iframe, but Microsoft no longer allows that, so the iframe shows a broken page. I’m tasked with finding a workaround.

My Idea

My idea is to make the portal open popup windows for Tableau and PowerBI authentication. After authentication has taken place, display the report in the iframe. But I don’t know how to detect whether authentication has taken place. Can anyone help me?