Thanks for taking the time to research this. I've read the instructions many times and feel the instructions aren't clear. The instructions say " report the total amount of deductions, credits,
exclusions, and exemptions related to certain trade or business activity for the
taxable year, as applicable." The deductions for 2020 were taken in 2020 so I would guess no Form 4197 needs filed in 2021 since there were no expenses for tax year 2021.