There are a lot of uncertainties about your situation. I think you need to consult a tax lawyer who has experience with aliens.
The following are some of the issues that might be involved, but don't take any of this as applicable rules or advice. I'm just trying to give you an overview of some of the complexities that your lawyer will have to resolve.
I don't think the expiration of your green card ended your resident status. You might have remained a resident alien until you filed the I-407. However, IRS Publication 519, U.S. Tax Guide for Aliens, page 4, says the following.
"Under U.S. immigration law, a lawful permanent resident who is required to file a tax return as a resident and fails to do so may be regarded as having abandoned status and may lose permanent resident status."
The fact that it says "may" suggests that there are additional considerations that are not stated, so the effect of the quoted sentence is uncertain.
If your residency termination date is in 2020, but not December 31, you were probably a dual-status alien for 2020, which has special tax filing requirements.
The United States might have a tax treaty with your home country that overrides the standard rules for determining whether you are a resident alien or a nonresident alien, including everything that I said above.
You might want to review Publication 519, particularly Chapters 1 and 6, before you talk to the lawyer, to give you an idea of what questions to ask.
