It's microwork, like Amazon Mechanical Turk. You sign up on a website and there are small tasks you can complete (label this picture, is this result inappropriate, which of these is better etc) and you get a cent. Sometime the task will really be a test and your performance will be evaluated. It sounds easy at first but you'll be asked to make a call on many edge cases but it's not worth spending more than a couple seconds on it. I've done it. I stopped because taskers were getting increasingly demanding, it got slower and more annoying and I wasn't interested in having to actually use my brain for 2€/hr.

My guess is, at that level of expertise, you're being scouted/recruited more than applying.

Or it's through Slack channels, like described in the articles.

Further, pretty sure they farm out most of these kind of jobs outside of USA/EU/Canada.

In places where it's legal to pay workers less than a dollar an hour.