TurboTax only goes back as far as 2019 so you cannot use a TurboTax product (unless you want to take a chance on a 2018 version from ebay or Amazon).
Otherwise, you can try contacting and enrolled agent to prepare and file the return for you.
See https://taxexperts.naea.org/listing/service/individual-tax-preparation
You can also get the forms from the IRS and prepare them manually if the return is relatively uncomplicated.
See https://www.irs.gov/forms-instructions
