The 10-year rule does not apply since your wife's mother died before 2020.
The late 2023 RMD must be completed now and will be 2024 income along with the 2024 RMD to be competed by the end of 2024. With the 2023 RMD completed, albeit late, a waiver of the excess accumulation penalty can be requested on 2023 Form 5329 as indicated in the instructions for Part IX of Form 5329.
While 2023 TurboTax can prepare the Form 5329 for inclusion in an e-filing of your tax return, TurboTax makes it almost impossible to do so when the individual requesting the waiver is under RMD age as in this case. It might be simplest to prepare the 2023 Form 5329 outside of TurboTax and include it with a paper-filed tax return. The 2023 Form 5329 requesting the waiver can also be prepared in forms mode of the CD/download version of TurboTax, but it could get deleted if one revisits the 1099-R section of TurboTax after doing so, so one has to be very careful when doing this.
