How do I get a 2020 EIN number as I’m self employed?
there is no such thing as a 2020 EIN. just an EIN.
you don't need an EIN to file a 1040. but you would want an EIN if you are issuing 1099s so you don't have to use your SSN. however, you will be subject to a small penalty if you are just now filing 1099s for 2020.