Anecdotally, I see Slack as something I use for professional purposes, and Discord as something I chat with my friends on. I have Slack on my work Mac, and Discord on my personal Mac. I see Slack as an extension of Skype for Business/Lync/other business tools, and I see Discord as a better Mumble/MSN Messenger.
They replaced Teams+Slack with Discord.
We quit that after screensharing was super low quality compared to Zoom — apparently (even paid for a Discord “server boost”, but no fix. I think it was an issue with the Mac client or something). I think one or two teams still use it, but for the most part everyone’s back to slack + Zoom now.
Zoom's screen sharing is really far and above all others. The quality is razor sharp (framerate suffers but who cares about that when sharing a terminal or document), the collaboration features are amazing (scribble on the content), it has so many useful niche features (draw on your ipad/iphone).
But these are all fairly informal use cases, initiated by individual academics and not by "the university".
It really doesn't target the enterprise customer, or even SMEs