You have a customer that needs to use Teams and other things. You either need to use what your customer wants in order to conduct their business, or you need to give up your customer. There's not a piece of software that is perfectly secure, there is not a place on the internet that is perfectly secure.
I understand your concerns about the possibility of malware, spyware, unnecessary cookies, and a whole host of other things that impact your security posture. These same things affect your customer's security posture. Mitigation takes on many flavors, not all of which involve avoidance.
The only completely secure computer is one that has been crushed into rubble, mixed with several yards of concrete into a big homgeneous pile has no power cable, no network connection, and has been thrown into the deepest part of the ocean. In other words, totally useless.