Student Loan Disclosure Transparency Act of 2021 This bill requires lenders disbursing federal student loans to disclose additional information to borrowers and increase the frequency of such disclosures. Specifically, prior to disbursement, the lender making a loan must disclose (1) the principal amount, interest rate, and number of required monthly payments to be made on the loan; (2) the estimated balance owed by the borrower; and (3) the estimated aggregate amount the borrower will pay. Prior to repayment, the lender must disclose the projected total of interest charges that the borrower will pay on the loan, as well as projections of the borrower's monthly repayment amount. The bill also requires certain disclosures for the life of the loan. In particular, lenders must disclose information about loans on a monthly, rather than periodic, basis. Lenders must also provide borrowers who are not in a repayment status (e.g., a borrower who is in school or in a deferment period) with a monthly statement. The Department of Education must obtain feedback from borrowers and report on the usefulness and effectiveness of such disclosures.