TurboTax can only generate Forms 8606 for distributions from traditional IRAs owned by Taxpayer and Spouse as participants. TurboTax does not have the ability to generate the separate Form 8606 necessary for the calculation of the taxable amount where Taxpayer or Spouse is the beneficiary of an inherited IRA. Inherited IRAs maintained for the benefit of an individual who is the beneficiary cannot be aggregated with that individual's own IRAs, so any taxable amount must be determined on a separate Form 8606 that you must prepare outside of TurboTax and then inform TurboTax of the result.
TurboTax has never supported Forms 8606 for inherited IRAs. If you have your own traditional IRAs, it seems likely that you filed in incorrect tax return for 2023 by treating the inherited IRA as your own. (If you inherited an IRA from your spouse and have chosen to treat it as your own, it's no longer an inherited IRA and would not have distributions reported with code 4 in box 7 of the Form 1099-R.)
