Matrix's moderation should be at least as good as Gitter. The GitHub integration is okay (it lets you create/comment/resolve issues using your GitHub identity from Matrix, and also can expose GitHub issues as Matrix rooms using https://github.com/matrix-org/matrix-hookshot). It's not quite as tightly integrated as GitHub was to Gitter though, but we're working on putting it in the Right Panel.

Some example Matrix communities which seem to work well include Mozilla (chat.mozilla.org), GNOME (https://matrix.to/#/#community:gnome.org) and KDE (https://webchat.kde.org/). Smaller ones include folks like Helix editor: https://matrix.to/#/#helix-community:matrix.org. I don't think anyone's written a guide for getting up and running though, which in retrospect is a crying shame; we'll get it on the todo list.

(p.s. thanks for Hex Fiend! :D)