Housing Fairness Act of 2020 This bill provides for testing and investigations to detect housing discrimination and awards grants to study the causes and effects of such discrimination. Specifically, the Department of Housing and Urban Development (HUD) must conduct regional or national testing programs and investigations to (1) detect and document differences in the treatment of prospective renters, homebuyers, or mortgage borrowers; (2) measure patterns of differential treatment because of the status of a renter, homebuyer, or borrower as a member of the protected classes under the Fair Housing Act (i.e., race, color, religion, sex, familial status, disability status, or national origin); and (3) measure the prevalence, nature, and extent of such discriminatory practices covered under the Act. Furthermore, the bill (1) eliminates restrictions on the use of fair housing initiative program-earned income received by qualified fair housing enforcement organizations after the grant period for such organizations ends, (2) increases funding for the fair housing initiatives program in FY2021-FY2031, and (3) requires HUD to study and report on the feasibility, efficiency, and effectiveness of converting the program into a specified noncompetitive, entitlement program. Additionally, HUD shall award grants to public and private entities to study housing discrimination, including the causes and effects of such discrimination. Finally, the bill prohibits the use of funds made available by this bill for any political activities, political advocacy, lobbying, such travel-related expenses, or for preparation of or provision of advice on tax returns.