Private Mattermost server. Advantages: Not indexed by search engines, not in the cloud, not a service that can go away at the whims of a corporation, not part a

Private Mattermost server. Advantages: Not indexed by search engines, not in the cloud, not a service that can go away at the whims of a corporation, not part a social network. Disadvantages: I have to maintain the server, it's not as feature rich as Slack, and it's one more program people have to run on their computers or phones.