When you have 1099 or self employment income you have to file a return no matter how small the amount. The 600 minimum is to receive a 1099NEC.
Self Employment tax (Scheduled SE) is automatically generated if a person has $400 or more of net profit from self-employment. You pay 15.3% SE tax on 92.35% of your Net Profit (If it is greater than $400). The 15.3% self employed SE Tax is to pay both the employer part and employee part of Social Security and Medicare (FICA). So you get social security credit for it when you retire.
You need to report all your income even if you don't get a 1099NEC or 1099Misc. You use your own records. You are considered self employed and have to fill out a schedule C for business income. You use your own name, address and ssn or business name and EIN if you have one. You should say you use the Cash Accounting Method and all income is At Risk.
Do you need to file a return? Yes if you have $400 or more in self-employment net earnings (gross income minus expenses)
https://ttlc.intuit.com/community/filing-and-paying-taxes/help/do-i-need-to-file-a-federal-return-this-year/00/25546
For Cash you enter it as Other self employment income or as Cash or General income. You don't need to get a 1099NEC or 1099K. Even if you did you can enter all your income as Cash. Only the total goes to schedule C.
You can enter Self Employment Income into Online Deluxe or Premier but if you have any expenses you will have to upgrade to the Self Employed version. Or use any of the Desktop CD/Download programs. How to enter income from Self Employment
https://ttlc.intuit.com/community/self-employed/help/how-do-i-report-income-from-self-employment/00/26653