I want to file 2019 returns

You cannot prepare a 2019 return online with TurboTax.   Online TurboTax is only for 2020 returns.

If you want to use TurboTax to prepare a 2019 return, you'll need to use 2019 desktop software (CD/download).   You can purchase 2019 desktop software directly from TurboTax as a download at this page and install it on your computer:
https://turbotax.intuit.com/personal-taxes/past-years-products/

You may be able to find the 2019 software cheaper at a reputable authorized retailer like Amazon, but even there be sure it is a legitimate authorized product from Intuit sold directly by Amazon itself, since there's no way to be sure all third-party sellers on Amazon are legitimate.   Here's a list of authorized retailers:

https://ttlc.intuit.com/community/choosing-a-product/help/where-can-i-buy-the-turbotax-software/01/2...

Be aware there are "too-good-to-be true" Internet scam sites selling fake or pirated software.  Only companies in the above FAQ are authorized for legit TurboTax downloads.   Some of them may no longer 2019 product.

Minimum system requirements for Windows version:
https://ttlc.intuit.com/questions/1901571-minimum-system-requirements-for-turbotax-windows-software

Minimum system requirements for Mac version:
https://ttlc.intuit.com/questions/1899173-minimum-system-requirements-for-turbotax-mac-software

The 2019 return cannot be efiled.  It will need to be printed, signed, dated, and mailed.  It's a good idea to mail by a method that has tracking, such as certified mail, priority mail, etc.

If you have both Federal and state returns, you need to mail each one separately to its respective tax agency.