TurboTax for 2018 and 2019 is no longer available, and no longer supported. Even if you find a copy of the desktop software somewhere you will not be able to use it.
Some other tax software companies may still have 2018 and 2019 available. Other options are to go to a local tax professional, or download the forms and instructions from the IRS web site and fill out the forms by hand.
In any case, tax returns for 2018 and 2019 cannot be e-filed, no matter how they are prepared. They have to be filed by mail.
