I'm not sure what you mean by "earnings." Your gross income for the year has to be less than $12,950. Gross income is not just earnings from working. It's your total income including interest, dividends, capital gains, pensions, IRA distributions, gambling winnings, etc., etc.
If you had $400 or more of business income or self-employment income you are required to file a tax return, even though your total income is less than $12,950. Driving for Uber, Lyft, DoorDash, etc. is self-employment income. Selling on eBay, Etsy, etc. has to be reported as business income if you have a profit on any of the items that you sell.
