None of the problems listed seem like problems to me. All of the solutions that make IRC fill this role seem like they will require more work and time to set up

None of the problems listed seem like problems to me. All of the solutions that make IRC fill this role seem like they will require more work and time to set up than I am to put in just to get communication set up. Slack just works. So unless I am going to be working on something highly sensitive that I can't trust a third party reading about, I'm going to keep using it. Wouldn't the best solution be to adapt one of the existing open source slack clients to use a local server? Then we have all of the feature set and none of the security and privacy concerns.