Self-employment is $10,000. $2,000 with a 1099-NEC & no 1099 for $8,000. Do I enter $8,000 on “other self-employed income”

Perfect!  When you enter the self-employment section you will have the option to [Add income for this work]. It may be toward the bottom of the page.

The screen will come up Let's enter any additional income for your work.

Select Other self-employed income includes cash and checks.

Simply continue through the interview.

If this does not completely answer your question, please contact us again and provide some additional details.

Actually I would just enter your total income as Other self employment income or as Cash or General income.  You don't need to get a 1099NEC or 1099Misc or 1099K.  Even if you did you can enter all your income as Cash.  Only the total goes to schedule C.