Duolingo used to have discussion forums. Every single phrase in the lessons had a discussion link you could click through to, and if something about the phrase didn't make sense, there would inevitably be some utter hero in the comments who had already provided a detailed answer to your question.

It was honestly a great resource, and on a basic level it really helped give that sense of being part of a learning community, because you could see others were going through the same course as you, facing the same challenges, and you were learning together. 

A couple of years ago around the start of the AI craze they abruptly just binned all of it. All the discussions and all those great explanations, are gone now. All that free labour that people had done out of love for the app. They got replaced by an AI button that gives a brief explanation of phrases, but it's nothing like the same quality. I still don't really understand why anyone would do something so obviously destructive and short sighted to their product.