Supporting Caregivers Act This bill reauthorizes through FY2024, and revises, programs and activities that support family caregivers of older adults. Among other changes, the Administration on Aging must disseminate best practices and award grants to states, institutes of higher education, and other organizations to conduct activities of national significance to promote quality and continuous improvement of services and other supports provided to caregivers. The bill also increases the cap on the amount of funds that a state may use to provide support services to older relative caregivers. In addition, individual area agencies on aging may exceed the cap, provided that there is a demonstrated need for the services and state spending overall remains at or below the cap for the fiscal year.