I would file an extension and then file the tax return in January or February.

The other option is to use the 2020 software, manually override everything to follow 2021 law, cross out "2020" and write "2021" on the forms, and file by mail.  Oh, and you can't really carry most things over from the previous year, so you need to either start from scratch or go and manually change everything for the one year difference (depreciation, balance sheet, etc.).

The first option will be much easier.