You are correct. You can amend the return, but not e-file it. As a side note, I also amended my 2020 return on March 26 and used TT to e-file that return. It is a month later and no sign of it on the IRS.gov/wmar website. According to TT it will take longer as they are still working through 2019 amended returns. Moral of the story: Don't make a mistake on your return or you will hate life!
