I use Linux in a corporate environment where Microsoft Office 365 is the toolchain of choice. One of the first things I needed to do my job was Microsoft Teams. Here are two things that worked for me.
The first (obvious) idea is to use the web UI. Messaging works out of the box with Chromium or Google Chrome. Getting audio and video calls to work is not obvious anymore. Basically, you need to pretend that you are on a Windows machine. This can be done by setting the “User Agent” to “Edge – Windows” with in the developer tools – see Christian Hujer’s blog post on the topic. Unfortunately, this hack breaks the message history. And there seems to be no way to get screen sharing to work. So while this solution is very easy, it is not optimal.
The second thing I tried and which works fine for me, is the unofficial MS Teams client by Ismael Martinez. I have it running on Ubuntu 18.04. As far as I have seen, everything works. Thank you!