if you filed before Turbotax was updated for the ARP act, the IRS will recompute your taxes and issue you a refund. it does not want an amended return unless you left something off that the IRS would not know about. if you filed afterwards, the nontaxable portion has already been calculated. you can tell by looking at schedule 1 line 8. if there is a negative amount on that line with the letters UCE, then you filed after the update.
the general rule is up to $10,200 is tax-exempt - up to $20,400 if a joint return and both spouses received UC or you lived in a community property state - and your modified adjusted gross income was under $150K.
There is no need for taxpayers to file an amended return unless the calculations make the taxpayer newly eligible for additional federal credits and deductions not already included on the original tax return.