I got a 1099-MISC from investment income, mostly box 8 "substitute payments in lieu of dividends. The software keeps trying to treat it as job income, what do I do?

You can enter your 1099-MISC as "Other Income" which will eliminate TurboTax from asking you about self-employment income. First, delete the original 1099-MISC that you entered, then enter it again. 

Follow the instructions in the TurboTax article How do I edit or delete a 1099-MISC? to delete your original 1099-MISC.

You can enter the income as “Other Income” so it won’t be subject to self-employment taxes.  Follow the steps below:

1. Open TurboTax
2. Select Federal Taxes
3. Select Wages & Income
4. select Start by Form 1099-MISC under Other Come Income
5. Select Yes to Did you get a 1099-MISC?
6. Follow the prompts to enter your 1099-MISC
7. Enter the reason to Describe the reason for this 1099-MISC 
8. Select None of these apply to Does one of these uncommon situations apply?
9. Select No to it didn’t involve work like your main job
10. Make your selection to How often did you get the income?
11. Select No to Did it involve an intent to earn money?

For additional information, review the TurboTax articles What's the difference between self-employment income and other income? and Where do I enter a 1099-MISC?