i have an iMac mid 2011. I cannot run TurboTax 2020 on the current operating system (High Sierra). However, it appears that I cannot upgrade this iMac beyond Sierra to Mojave. true? if so, any other options?

If you can load the online version of Turbotax it is a far better deal. Once you sign up, you can use it year after year and it remembers your data. Plus unlike the store bought CD's, it is always up to date.

FWIW, it is correct that you cannot upgrade beyond High Sierra.

I believe Intuit has an online version of TurboTax.