I like @win8linux and @PulkoMandy’s ideas of having bridges from Discord connected to either IRC or Matrix. Whether we need another service such as Matrix is dependent on whether we as a community or the Inc. need a space to hold virtual online meetings. Otherwise, the current platforms for communication are fine.
As @MrEntropy has helpfully pointed out there is an existing Discord server for Haiku which we can reuse:
Discord Server
For the convenience of everyone else, we will probably need to improve the server by adding bridges to IRC (and Matrix if we need such a service), moderation bots and perhaps setting up some server rules (no swearing, spamming, “flaming”, etc.)