You have the option to keep the inherited IRA in the name of your deceased spouse, in which case the non-deductible basis must be tracked on a separate 8606 form that cannot be prepared by TurboTax - you must download the 8606 from the IRS and manually complete and mail it for the inherited IRA.
You also had, or have, the option to treat the IRA as your own as surviving spouse and have the trustee of the IRA put it in your name or do a trustee-to-trustee transfer (not a rollover) into your own IRA. Then you would track all the basis on a single 8606 form. Your RMD would also be based on you and not your spouse.
See:IRS Pub 590B
Surviving spouse. If you are the surviving spouse who is the sole beneficiary of your deceased spouse's IRA, you may elect to be treated as the owner and not as the beneficiary. If you elect to be treated as the owner, you determine the required minimum distribution (if any) as if you were the owner beginning with the year you elect or are deemed to be the owner. For details, see Inherited from spouse under What if You Inherit an IRA?, earlier in this chapter.
I inherited a traditional IRA from my deceased spouse with a nondeductible basis and I did a spousal rollover into my traditional IRA which has a nondeductible basis. Since I comingled the assets I combined both nondeductible basis together. Can I just file one Form 8606?
If the assets have been comingled, the inherited IRA is no longer an inherited IRA but is instead now an IRA owned by the surviving spouse and all distributions, basis and year-end values would go on the surviving spouse's Form 8606 that can be prepared by TurboTax.