Can I include a schedule SE with $0 due (business loss) in my electronic return even if TurboTax default is to exclude it?

Yes, Schedule SE for Self-Employment tax should automatically be included in your return, even if you had a Business Loss on Schedule C.

You can visit the Schedule SE section in TurboTax by:

1. Open (continue) your return if it isn’t already open.
2. Inside TurboTax, search for sch SE and then select the Jump to link in the search results.
3. On the Self-Employment Tax screen, select Make Adjustments. 
4. Make sure you have entered your Business Income/Expenses first. 

This year, there is an option to exclude a portion of SE Tax due to Covid, so TurboTax wants you to make an entry on Line 18. This may be causing your error.  Try entering $0 there. 

Click this link for more info Schedule SE.

This link gives more info on Self Employed Tax Relief.