2020 software isn't available anymore, unless you already purchased it previously. Here is a link to paper forms: 2020 Form 1040 (PDF)
It is important to file an unfiled return because there is no statute of limitations on an unfiled return. You can file a past due return anytime, but you only had 3 years from the original due date of 4/15/2021 to claim a refund, if you were due one. Because 4/15/2024 has passed, unfortunately, it is too late to get a refund. See: Claim a refund However, if you owe taxes, filing will stop the accumulation of penalties and interest.
