Is Slack still around?
Our local 'Digital' guru (or Mr. Fancy Pants' as another article described these people) went on a drive to push Slack about a year or so ago. Everyone was encouraged to 'get collaborating' and we had to access it via Chrome, until a Chrome update killed it and/or we breached the 'free usage limit'.
This is the first I've heard of it again in at least ten months . . .