Start new chat in MS Teams desktop is not intuitive and hard to find as it's on it's own (top left) with no association to chat and not in a logical spot - did you do any user testing on this...I'm not a power user and always frustrates me to find it.

It should be located as an option on chat menu item on left; and or top right where you can add people to a chat..

This is UX 101 stuff, come on MS