You can use the TurboTax 2019 online editions for test purposes since there is no payment required unless you want to the print or e-file the tax return.
Or you can use the TaxCaster calculator to do estimates - https://turbotax.intuit.com/tax-tools/calculators/taxcaster/
If you used the "Online" software for your 2019 taxes........just don't use the same "Online" tax account that you filed your 2019 taxes from...only use a new account.
..................(or better yet...use desktop software every year, that allows you to have different test files , and even a special "What-If" worksheet in the current tax return that allows you t see what would happen the next year, but without destroying your current tax file)
Here is another tool to play around with https://www.mortgagecalculator.org/calcs/1040-calculator.php