TurboTax Deluxe 2020 requires macOS 10.14 or higher and I only have 10.13.6.
Option 1 ... get a new MAC
Option 2 ... use the Online version https://turbotax.intuit.com/personal-taxes/online/
You can use online TurboTax if your computer does not meet the system requirements for desktop software.
ONLINE 2020
https://turbotax.intuit.com/personal-taxes/online/