I received an IRS tax refund for 2021 in 2023 (CP24), plus interest (CP21B). Where do I report this in Turbo Tax Premier?

Enter interest from the IRS like a 1099Int and put the amount in box 1. Enter it manually and just enter IRS for the payer. Don't enter any other info like the address or a EIN. On the Let Us Enter Your 1099 page go down to the bottom and pick Enter a different way

Federal
Wages & Income
Interest and Dividends
Interest on 1099INT - Click the Start or Update button

Put the interest amount in box 1

Thanks, but most of the money  isn't interest, it's labeled as a refund.

You just report the interest, not the refund part.  

Thanks, but most of the money isn't interest, it's labeled as a refund. So, it should be a Federal Refund or, perhaps, Other Income, but TT doesn't include a Federal Refund as an example of Other Income.

Ah, that is very helpful. Thanks!

I'm not sure why you are stuck.  Do you know how much is the interest?  Just enter the interest part.  You do not enter a federal refund anywhere.  Interest goes under Interest like bank interest.