First, only the person with whom the child lived more than 50% of 2020 can legally claim her. You can still file a tax return with no income (add $1 of interest), and maybe get the stimulus. Did you have no income at all in 2020? If someone else supported you (say, your parents), they can probably claim both you and your daughter as dependents. If more than one person claims her, the IRS will investigate. Also see this:
How Do You Report Suspected Tax Fraud Activity? | Internal Revenue Service (irs.gov)
(And see Legal Aid about getting child support.)