Which is unfortunate, but a consequence of Microsoft's perennial, embrace, extend, extinguish - they embraced instant-messaging version 3 (or wherever we are now), and they're onto the extend part - extending Teams' reach by bundling it 'for free' in Office, and the OS, so people don't "need" to buy Slack.
Slack won't be 'extinguished' but it will have a falling market share, despite the dumpster fire that is Teams, and the bean-counters in most corporations getting kudos from their bosses for 'cost savings'.
Frequently fails to connect, doesn't honor system audio device settings and frequency forgets its own, frequently fails to mark messages as read, sometimes even after hitting "Mark all as read," sometimes fails to send notifications on new chats, especially on my phone.
It's the least reliable chat program I've ever used.