I vaguely remember something about TurboTax not including a completed Form 8606 for Spouse at some point in the past. It might have been in 2018, but the problem was rather quickly corrected and only affected early filers, I think. Unfortunately I don't have any notes on this particular issue.
If your 2018 tax return did not appear include the Form 8606 for Spouse but does show Spouse's nondeductible contribution on the IRA Contributions Worksheet, I would confirm that it is absent from your 2018 Tax Return transcript from the IRS, then file the missing Form 8606. You can probably file it stand-alone, but filing it with Form 1040X provides a place to include explanation that the tax software appeared to simply fail to include the form despite having made the appropriate entries.
