You can file a tax return showing zero income and claiming the rebate, if you did not previously receive the stimulus payments from the IRS.
Because e-filing is closed for 2020 and 2021, you would have to print your returns on paper, sign them and mail them to the IRS. If you want to buy TurboTax for this purpose, it will cost you about $60 for each year. You may be able to find a VITA office or other tax assistance program through your local social services network to help you file for free. Or you can do it yourself on paper if you download the forms and instructions. It's not hard if you have a simple return.
You should expect that paper filed returns will take at least three months to process before the IRS can issue a refund or a rebate check.
