I reply to you but that’s more targeted about the indexation problem.
It is true that using discord as a forum would make it harder to index. And that we already have this discourse forum. But why not imagine something hybrid where we could mirror the content of such discord forums as threads in discourse. That way we can link both services through a bot or something, and replicate the content of the discord forums on the website.
By so they would get indexed and accessible through any search engine.