If you make video call or join a meeting with Teams and have your camera turned on, you can now hide your own video.
To do it, just open the ellipsis menu (you know the 3 dot …) and select Hide for me
Doing so, your video feed will be minimized and you can show it again by hitting the arrow (location may vary if you are on a video call or meeting).
Unfortunately there is no default settings you can configure and you can not neither do it while joining the call/meeting.