My husb & I file Schedule c's. We purchase health insurance for ourselves without subsidy (not through Marketplace). We enter the cost of premiums Sched. C, D or both?

The premiums should either be entered as a self-employed health insurance deduction on line 29 of Form 1040, or as an itemized medical expense deduction. If you qualify for the self-employed health insurance deduction, that will be the most advantageous use of the expense. See the following from TurboTax Tax Tips - Deducting Health Insurance Premiums If You're Self-Employed:

To enter in TurboTax if you are filing a Schedule C:

1. Go to the Business category.
2. Go to the Business Income and Expense subcategory.
3. Choose the option "I'll choose what I work on"
4. On the screen labeled "Let's gather your business info", find the section labeled "Less Common Business Situations".
5. Click start or update next to the line labeled Self-employed Health Insurance.

Thank you...I of course meant Schedule A, not Schedule D in my question

And TurboTax should make mention when you enter the Self-Employed Health Insurance Deduction that you then should not enter it again under personal deductions, since it doesn't automatically stop you from doing it