Everyone uses Form 1040 this year, but that is not the reason it is suggesting an upgrade.  The credits you will be receiving are on one of the new Schedules 1-6, which would require an upgrade if you continue in that product.

I'll tell you about another free product you may qualify to use that can handle all the forms without any upgrades or fees.  I'll first explain what is happening, then at the end of this post tell you about the other free product, which is free for both Federal and state returns.

If you are reporting any student loan interest or receiving any credits, those are some common things that would require someone who normally uses Free Edition to have to use Deluxe, since they require a new Schedule.  But I'll tell you about a second free product below.  So read the whole answer first.

Because of new changes in the tax laws for 2018, there may be some filers who can no longer use the regular Free Edition this year.   The regular Free Edition is more limited this year due to tax law changes.    If you need any of the new Schedules 1-6, for instance, then you can't use Free Edition.    You can read about the new schedules at the link below.  If you click the "more info" link there, it will show you what each schedule looks like.

https://ttlc.intuit.com/questions/4511015-what-are-the-new-schedules

Here are some common things that cannot be handled by the regular Free Edition:

     Itemized deductions
     Business or 1099-MISC income
     Sales of stocks/mutual funds/bonds
     Rental property income
     Foreign Earned Income
     HSA
     Credits, deductions and income reported on the new schedules 1–6, such as the Student Loan Interest Deduction

TurboTax has another free product called the TurboTax Free File Program.  It is free for both Federal and State--IF you meet just one of the qualifications.   It can handle all the usual forms without the limitations of regular Free Edition.

See this FAQ to see if you meet one of the qualifications:
https://ttlc.intuit.com/questions/1900583-what-is-turbotax-free-file-program

The TurboTax Free File Program is located at the link below.  It requires a new User ID from what you are currently using for Free Edition since it is a different website, and the IRS requires it to be disconnected from the TurboTax commercial products.
https://turbotax.intuit.com/taxfreedom/

If you decide to switch, here's how.  Note you will need a new User ID, different than Online TurboTax.
https://ttlc.intuit.com/questions/2026912-how-do-i-switch-to-turbotax-free-file-program

If you want to look at your Schedule 3 to see what credits you are qualifying for, here's how:

While your return is open, click in the left menu column on TAX TOOLS, then TOOLS.
Then at the Tools screen click on "View Tax Summary."
At the Tax Summary screen go back to the left menu column and click "Preview My 1040."
That will open the 1040 Worksheet.
You can view the 1040, then scroll down to the schedules below it and find Schedule 3.
It should show you the non-refundable credits you qualify to receive.