The actual Turbotax program is only designed to prepare a current-year return. So far, there have not been any major changes to retirement income taxation for 2021, so using the 2020 program will give you a reasonably close estimate. You can use Turbotax online for "free to start", and input your details, etc. But if you want to see the detailed results you would have to pay.
The Turbotax Taxcaster is also free to use and you can easily make adjustments to test different situations. It's also based on 2020 laws but the results should be similar for 2021.
The IRS forecaster is more geared toward helping workers adjusts their W-4s, but should also work for retirement.
