I agree with @dmertz in that the code "R" seems inappropriate for what happened here.
I'm not absolutely sure what year the taxes were paid in for, but the 20201099-R would notify the IRS that they were paid in for 2020 one would think.
Because of the "R" code, it would be appropriate to report the distribution in 2019 by amending your tax return. However, if the taxes paid in were reported in 2020, you may find when you submit your 2019 amended return, that you don't get credit for the taxes paid in, as they were probably applied to 2020. You may instead get them refunded when you file your 2020 tax return.
In any case, you should report the 1099-R on your 2020 tax return, since the IRS will get a copy of it and may want to know how you handled it in 2020. And you should report just the details on your 2019 tax return, assuming the form 1099-R does not duplicate anything reported on the original form 1099-R.
[Edited 3/3/21 2:38 PM PST]
@harvey_schwartz
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