Microsoft Teams does not have a “true” fullscreen mode. Even if you select both “focus” and “fullscreen” there is always a command bar left at the top. This can make it difficult read small text when people are sharing their (high resolution) screens. Here are two tips how to improve:
1. Pressing Ctrl+Minus will make the Teams GUI smaller. Do this multiple time. Each time the shared video gets more room! (You can always press Ctrl+Equals to go back to 100% zoom.)
2. Use the web version of Teams instead. This actually has a *real* fullscreen mode. (It’s not a problem to have both the web version and the ordinary desktop client running at the same time!)
As a side note: From time to time I’ve had problems with viewing screen shares in Teams. The framerate of the incoming video is extremely bad and drops to something like one frame per *minute*. In these cases I have had better result using the web version instead of the ordinary client. Still not super fluid, but at least good enough so you can follow the conversion.