I’m trying to file a 2019 return, but cannot find the software. Help?

To complete and file a 2019 tax return using TurboTax you would need to purchase, download and install on a personal computer one of the 2019 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/

A 2019 tax return can only be printed and mailed, it cannot be e-filed.

Do an internet search for it.  I just found Turbotax Deluxe State +Federal for 2019 - for Mac and Windows - listed on eBay for $19.99 (today is 8/1/2021).  I haven't checked Amazon, but it's probably available there, too.

Just in case you need this....

Window System Requirements

https://ttlc.intuit.com/community/system-requirements/help/minimum-system-requirements-for-turbotax-windows-software/00/26175

Mac System Requirements

https://ttlc.intuit.com/community/system-requirements/help/minimum-system-requirements-for-turbotax-mac-software/00/25609

How to install on Mac

https://ttlc.intuit.com/community/installing/help/how-do-i-install-the-turbotax-software-for-mac/00/26067

How to install Turbo Tax on Windows

https://ttlc.intuit.com/community/refund-status/help/how-do-i-install-the-turbotax-software-for-windows/00/25934