You received the 1099-R form in 2020 because that is when the distribution was made for the repayment of your excess contribution made in 2019. Since the contribution was made in 2019, you have to amend your 2019 tax return.
You need to amend your 2019 tax return and enter the distribution on that tax return. To report the earnings on the excess contribution, you should enter the 1099-R on your amended return.
Enter in box 1 the distribution amount. In box 2 enter the earnings. Enter code "P" and "J" in box 7. Work through the questions in TurboTax after you entered the 1099-R until you see a question regarding why you made the distribution, to which you will respond it was a return of an excess contribution.
[Edited 3/11/21 12:06 PM EST]
@TAXPERPLEXED
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
