The best setup is for the community to use multiple platforms to share information, not just one. So you'd have the issue tracker for the project, a forum for public discussions, a wiki for the documentation side of things and Discord/Slack/Matrix for more casual discussions.

Ideally you'd then take any discussions that deal with topics the public might be interested in and encourage the participants to continue them on the forum instead, and move any resources shared on the server to the wiki for the same reason.