Tribal Trust Land Homeownership Act of 2021 This bill sets forth requirements for the processing of a proposed residential leasehold mortgage, business leasehold mortgage, land mortgage, or right-of-way document by the Bureau of Indian Affairs. The bureau must notify lenders upon receipt of such documentation, perform a preliminary review of such documents not later than 10 days after receipt, and approve or disapprove of such documents within 20 or 30 days, depending on the type of application. Additionally, the bill sets forth requirements for the bureau regarding (1) response times for the completion of certified title status reports, (2) notification of delays in processing, and (3) the form of notices and delivery of certain reports. The bill also provides relevant federal agencies and Indian tribes with read-only access to the Trust Asset and Accounting Management System maintained by the bureau. The Government Accountability Office must report on digitizing documents for the purpose of streamlining and expediting the completion of mortgage packages for residential mortgages on Indian land. Finally, the bill establishes within the bureau's Division of Real Estate Services the position of Realty Ombudsman.