If your only income was SS benefits then you only need to file a 2020 return is if one or more of these apply :
1) you are filing separately from your spouse and you lived together at any time during the year
2) you had insurance thru the Marketplace (Obamacare) and got a 1095-A in January
3) you had fed or state taxes withheld
4) you did not get the stimulus check in 2020 or did not get the full amount for any dependents
