According to TurboTax IRS forms availability, the amended form will be available in TurboTax on 3/25/21.
https://care-cdn.prodsupportsite.a.intuit.com/forms-availability/turbotax_fed_online_individual.html
You can't file an amended return in TurboTax right now because the IRS has to approve their form that goes in the software so you can e-file. You can get the 1040X form on the IRS if you want to manually enter your amended information & then mail it in.
To add: The IRS right now is handling tax return processing since they only started accepting returns on 2/12/21.
