If you do not have the situations covered in the Premier Edition, you can revert back to Deluxe by using the Clear and Start Over feature (you won't be able to do this if you've already submitted payment or deducted the TurboTax fee from your refund).
While you’re welcome to downgrade, you may miss some features—and you’ll be prompted to upgrade when those features are needed.
That's sort of a stupid non-answer answer.
Be careful trying to use the Fidelity link to TurboTax. I tried it to get the discount and TurboTax auto-upgraded me to Premier, which I don't need, nor had I used any of the features (nor will I use any of the post-tax options). I was so careful throughout not to trigger Premier, but the Fidelity Link seemed to do it. You cannot downgrade without starting over entirely!! I'm not going to spend the time typing it all in again, but I will remember to switch software next year.
Needing to start over may protect TurboTax from folks who have used some of the functionaility, but after 20 years with TurboTax, I'm definitely moving on next year.