I read this a few years ago.

Time Exclusive: OpenAI Used Kenyan Workers on Less Than $2 Per Hour to Make ChatGPT Less Toxic

https://time.com/6247678/openai-chatgpt-kenya-workers/

Beyond that, I think the reason you haven't heard more about it is that it happens in developing countries, so western media doesn't care much, and also because big AI companies work hard to distance themselves from it. They'll never be the ones directly employing these AI sweatshop works, it's all contracted out.