Microsoft already claimed it would run in a browser but my experience was that this was only the case if the browser was MSIE/MSEdge/Chrome running on MS-Windows - certainly not Firefox or Chromium on Linux. I didn't try Apple or Android platforms but several of my colleagues seem to be using it on Apple Macs without issues. If you Google for instructions you'll (eventually) find a description of how someone made this work on Chromium/Linux with a lot of tweaks - this didn't work for me. Sorry - I would have provided a link but I didn't make a note of it and its hard to find.
I am currently running MS Teams 1.3.00.5153 on Linux Mint 18.1.
Apart from the following issues, it mostly works...
- does not send video (receive is OK)
- cannot show my desktop (same issue as above?)
- sometimes it stops communicating with my microphone
- steals focus every time a new chat arrives (by far the most annoying bug)
- does not add an XDG start menu entry
- does not shutdown nicely at logout
It's FOSS software, the client runs in a browser, and there are optional clients (I'm guessing HTML apps) for iOS and Android.
I can't say how compatible/stable this will be - but OMG! what a neat looking bit of software. It has built in recording and POTs integration. But what I really love about it is the hand icon.