You won't be able to file your 2021 tax return until sometime in late January. By then, TurboTax will be updated for the third stimulus payment.
The early releases of any tax software for the new year are really just a rough draft. A lot of things aren't included yet, and a lot of things haven't been updated yet from the previous year. These things will be taken care of in updates over the next couple of months. The IRS has not even announced a date when filing 2021 tax returns will start, but it will be sometime in late January.
