Yes. You mist file a 8606 for ANY non-deductible Traditional IRA contribution or it will n ot be allowed to be used in the future to offset tax on distributions.
If you enter the Roth contribution as a Roth contribution in the TurboTax IRA contribution interview and say that you switched it to a Traditional IRA and did not deduct it then TurboTax will automatically add the 8606 to your 2019 tax return. If you already filed 2019 then you will need to download a blank 8606 from the IRS forms site and manually fill it out and mail it to the IRS.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**