On Windows I have switched to Edge for Teams.

That seems a bit too conspiracy theorist, especially considering most people have 3rd party cookies on and teams has been around for a long time now (I assume before Google announced removing 3rd party cookies)

I think the answer is more banal in that some of their oauth flow runs in a different domain from the main application. I think this is tied to wanting to reuse part of oauth flow in the desktop application.

The auth flow for Teams has always been very buggy so that is a good guess.

The funny thing is that they actually have a specific error message for this asking you to enable 3rd party cookies. I guess it is easier than fixing the issue.

Microsoft auth flows are such a dumpster fire that it makes me curious about how it got to be that way.

> That seems a bit too conspiracy theorist

Remember "DOS Isn’t Done Until Lotus Won’t Run"?

That large companies do self-serving underhanded tricks is not a conspiracy, just yet another Monday in the office.