Technically yes, you do have to report them regardless of the amount, but the real risk depends a lot on what country you live in - some have automatic agreements with those platforms and others don't, so first thing you need to do is find out what specifically applies in your jurisdiction.
What not many people mention: a lot of times it's worth opening a bank account in your name and putting the income there instead of leaving it on the platform, because bank transactions leave a much clearer trail than if everything just sits in Upwork. If you ever get audited, it's easier to prove legitimate income when it's in your bank than when it's saved in the app. Then you just report it using your bank statements and you're done.