To complete and file a 2021 tax return using TurboTax you would need to purchase, download and install on a personal computer one of the 2021 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
A 2021 tax return can only be printed and mailed, it cannot be e-filed.
I can't speak for TurboTax specifically. But IRS accepts e-filing of tax returns for the past 3 tax years.
@guywong You cannot e-file a 2021 return from the do-it-yourself TurboTax software. If you are using TurboTax for a 2021 return--you file it by mail.