Mac client for Microsoft Teams not letting me sign in

I am trying to get Microsoft Teams running on a Mac, it seems to work fine from the web, but the Mac app gives me something else entirely, won't let me login:

From the web (Edge):

From the app:

Default browser is Safari, if that is a factor.  I get some other message there, apparently something about Apple's security setup there, but Teams is working under Edge, at least to the extent shown above.  When you launch in Safari, it says to run the App, but then when I download and run the App, it won't login.

Suggestions?