[toastercat]

I think you're missing the context of the thread. An open-source project doesn't need to choose a tool that competes with Discord in popularity -- popularity is not important here. The aim is not to attract millions of users, the aim is to provide a valuable and sustainable resource to its community that it can link in the project's README file. A tool like Discourse or Zulip is more sustainable than Discord because they are open source, history is exportable, and the software is trivially self-hostable in case the managed hosting solutions don't pan out.