Broadband Reserve Fund Act of 2021 This bill establishes the Broadband Reserve Fund into which the proceeds from certain spectrum auctions must be deposited. The Federal Communications Commission and the National Telecommunications and Information Administration may use the amounts in the fund if Congress specifically authorizes the spending. The bill also expresses the sense of Congress regarding the purposes for which amounts in the fund should be used, including (1) broadband deployment to unserved areas, (2) distance and remote learning, (3) securing the telecommunications supply chain, and (4) telehealth technologies.