It still competes with SO because now you'd post the question about a certain framework or library on its repo's discussions. Also, isn't it kind of explicitly doing that because discussions can elect an "accepted" answer?

Yeah, but way more people look for answers rather than ask them (not to mention the pain of having to answer the same question repeatedly if they can't find the answer).

Accepting an answer is an attempt, but without the moderation, editing, voting, duplicate closing and so on from SO, the quality and ease of finding answers won't be there.

I'm sure plenty of people remember trying to find answers through forums, and it was a nightmare. The thread might not actually have an answer in it, and even if you get pointed to an answer, it'll often need context from the rest of the thread, it might be out of date, or completely wrong.

To put it simply: there is a reason why people use SO almost exclusively for Q&A, and there is a reason people still use forums and stuff as well. Discussion and Q&A have different goals and conflating or combining them leads to pain for users.

It’ll be very interesting to see how Google ranks the search results. I don’t know about others, but I almost never directly search SO, and almost always end up there through Google. If GitHub Discussions has the answer and Google directs me there, I will definitely not visit SO as often anymore.

Stackoverflow's search algorithm sucks compared to Google. I always use google and add the "site:stackoverflow.com" operator to find answers on SO.

To be fair pretty much everybody’s sucks compared to Google. I think your approach is almost universally sensible.

I've found the questions that SO surfaces when writing my questions to be pretty good.

even though many projects actively try to dissuade "user" questions and direct you to SO. Now they'll maybe send you to the relevant discussion. This is closer to the "source" for answers specifically linked to one repo or project. For more general questions, we'll see if GH broadens what discussions can be used for; if there will be a place for more general topic discussions

It looks exactly like SO to me. There is a question, it is voted on, and there are answers, with one selected as the correct answer. There is no reading through the entire thread or anything like what you are suggesting.

It also competes with Reddit.

I am a long time user of SE (questions and answers alike) and I go to reddit for questions which are more vague (because I do not know where to go) or the ones which invite discussions.