In our company we have experienced multiple times a problem with MS teams links. Specifically, when user clicks on MS teams link, system should open meeting log in page where it prompts for an username, but instead it opens MS account log in page. These links usually are sent from outside (partners, clients etc) and not all users have MS teams accounts under our organization (im not sure how its properly called). When I myself create a meeting and send our people Teams link, never i have seen this problem. I have tried to understand it, but i fail and this is one of the things that drive me mad about all social distancing apps.
This problem can occur on both web based and desktop based Teams clients. Sometimes it occurs only on one of them. No consistency here.