The only way to downgrade is to clear and start over, but you must have entered something that requires self-employed like a 1099-NEC.

How do I clear and start over?
https://ttlc.intuit.com/replies/4248526

Or one thing you can do is buy a lower version of the Desktop program like Deluxe.  All the Desktop programs have the same forms.  You just get more help and guidance in the higher versions.  Then you can switch from Online without starting over.  You can download the .tax2020 file from online for free and open it in the Desktop program (any version).  And the Desktop program has several other features and benefits over the Online version too.

See the Desktop CD/Download program prices here.  You also get 1 free state program download.

https://turbotax.intuit.com/personal-taxes/cd-download/