using a second external camera with microsoft teams

Its not ideal but I have a mobile phone on a bendy bracket with Teams installed on it. The phone joins the meeting as well as my PC so I have 2 viewpoints. I use one for delivery and PowerPoint presentation, and the other to view my actions, be it writing on the whiteboard or doing detail work on the desk. Before each session I set the camera up to be the view I will need for that lesson. Similarly to yourself, I teach material science and find it really useful when trying to show students how to do things. I hope this helps.

My solution for this problem is to join the same session with the same account from two devices. E.g. show you with the camera in your smartphone and show the teaching content, whiteboard, experiment or whatever with a camera attached to your notebook. Make sure to mute microphone and speaker on one device and keep microhone open on that device that streams the video that you want to show in large screen, because teams shows the video in large where the noise comes from. You can also attach an external microphone in addition to the one that comes with your webcam. Plus, I recommend to attach both devices to a power supply for longer sessions.

OBS is a good solution. Doublecheck with your participants whether they see the video mirrored or normal. Usually you as a presenter see the video mirrored and the participants see it normal.