You can also choose to include sound (or stop including it) after you've already begun sharing your screen.

You might need to pause or play your video content to start sharing sound, or try the Include computer sound switch on the top left of your sharing options again if the driver fails to install. Once the driver is installed on your Mac, you'll see a notification at the top of your meeting controls. Just follow the simple wizard and click Install or Update. It takes about 10 seconds for the installation to complete. On a Mac, you will need to install a driver the first time you include computer audio in a Teams meeting. Adjust your computer’s audio output in your system settings, and your Teams audio output in your device settings in Teams.

Note: Teams and your computer need to be set to the same speaker.