Are you looking for personal tax help, or is this for a client? You stated "my broker."

"However. I'm not sure how to handle the 2 other distributions for 2017 & 2019."

Those are all part of 2020 tax return, if you got to them before 2020 is filed. The 1099-R distribution will be for 2021, but the activity is for the prior tax year.

"On my 2021 tax return I would then not have to pay any 6% penalty at all. Based on the info from the broker no earning is calculated on either the 2017 or the 2019 Distributions. Is my thinking on this correct?"

No. Well, unless your total of all deferred account types took a loss over all those years, of course.

Go to the IRS site and read the instructions. Learn how the prorata computations are described. I also like to read the investment house instructions for how to handle excess, since they are communicating to regular non-CPA taxpayer investors.

It seems it's time you learned this more thoroughly for your own needs and for your clients' needs.