Step 1: In your mail app, open the invitation email, press the Tab key until you hear “Open Microsoft Teams,” and press Enter.
Step 2: The Sign in to your account page opens in your browser. To accept the invitation, press the Tab key until you hear “Accept,” and press Enter.
Step 3: In Microsoft Teams, to switch between your regular organization and the organization you’ve been added to as a guest, press the Tab key until you hear “Signed in to,” followed by the name of your organization, and press Spacebar.
Step 4: Press the Down arrow key until you hear the organization you’ve been added to as a guest, followed by “Guest,” and press Enter. You can now access the team you’ve been invited to as a guest.