if the IRS was tardy in issuing your 2020 refund, it is required by law to pay you interest. the interest would have been included with the refund. it is taxable. if the first two EIN numbers are 38 and the last 4 are 8424, it's probably what I indicated above. I don't know if it uses other EINs
you should be worried more if it isn't from the IRS. that form has your SSN which would mean it could be on the dark web and you are a victim of identity theft.
you could call the IRS or check your IRS transcript to verify.
