Did anybody try selling a service like this:

Your our own instance of Mattermost, Discord, or any well know service like those. We manage it for you on our servers, keep it running and up to date. You have admin access to the web app, not to the server. Pay per seat? You can get a db dump at any time and start it over somewhere else.

Basically it's what we get from Slack but we would really own the data. We must trust the service provider but those machines are already in somebody's else cloud, so not a big change.