Where do I enter a military survivor annuity amount shown on a 1099-R?

You'll enter it just as you would any other Form 1099-R.  See the TurboTax Help article Where do I enter my 1099-R? for entry guidance.

In Box 7 of your Form 1099-R, Code 7 indicates military pensions or survivor benefit annuities. See Military retirement annuities in the 2023 Instructions for Forms 1099-R and 5498 for more information.