For information regarding Appraisal Bias/Discrimination:
If you feel you have been a victim of appraisal bias, you can submit a complaint with HUD's Fair Housing and Equal Opportunity office to get help. https://www.hud.gov/program_offices/fair_housing_equal_opp/online-complaint
If you believe a lender discriminated against you, including by using an improper appraisal, you can submit a complaint to the CFPB. https://www.consumerfinance.gov/complaint/
The Department of Justice, Housing and Civil Enforcement Section, also enforces the Fair Housing Act. The Department of Justice brings suits on behalf of individuals based on referrals from HUD. https://www.justice.gov/crt/fair-housing-act-1