As far as I'm aware Slack does not offer on-premise installs. (On-premise in this case could mean running in my own account at a cloud service provider) It's unfortunate because I'd love to adopt them as well at my current company, but it will be very difficult to achieve if the only option is to become yet another tenant of some large multi-tenant infrastructure.

Microsoft will quickly take over this market if they offer an easy-to-manage on-prem solution that's integrated with the company directory, as it seems they've done. Plenty of firms already have Exchange and ActiveDirectory and Skype for Business.

I think this is one reason teams use hipchat, because it does provide this.

Correct me if I'm wrong, but Microsoft Team doesn't currently have a self-hosted option. I hope it's in the pipeline because my company can't use an offsite IM service. It would be nice if Microsoft added support and then Slack followed. Competition is good!

Mattermost is an open source, self-hosted Slack-alternative: https://www.mattermost.org/what-slack-might-learn-from-its-o...

There is also Matrix (matrix.org), an open standard for decentralized communications. Our goal is to let all apps talk to each other - including Slack, Mattermost, and Microsoft Teams!

Check it out using any Matrix-enabled app: https://matrix.to/#/#matrix:matrix.org

Skype can be self hosted.