Supplemental Security Income (SSI) payments are not taxable income and are not reported on your income tax return.
You are entitled to file a 2020 return even if you had no taxable income; if you did not receive a stimulus check in round 1 ($1200, April-July 2020) or round 2 ($600, December 2020-February 2021) then you would get a recovery rebate on your tax return. You may need to create $1 of fake bank interest before you can file, since you can't e-file a tax return with no taxable income. (This work-around will not cause problems with the IRS, they know about it and it won't change your tax.)
If you already received the stimulus checks, you won't get more by filing a return.
