Deductions & credits

You are correct - it is deductible Just enter it as an "Other Medical Expense", the last screen in the Medical Expenses interview (see sample screenshot, below).

From  Publication 502 (2020), Medical and Dental Expenses:

Certain improvements made to accommodate a home to your disabled condition, or that of your spouse or your dependents who live with you, don't usually increase the value of the home and the cost can be included in full as medical expenses. These improvements include, but aren't limited to, the following items.

• Constructing entrance or exit ramps for your home.