> Turn off all notifications except the unread messages count badge and check it when it overflows.

...then keep a straight face while your super Agile manager berates you in front of the entire team because you're hard to communicate with, we have Slack for a reason.

Not everyone has the choice to not allow Slack to interrupt you. Some organizations mandate this sort of communication, disruptive though it may be.

Edit: just to clarify, I'm not in this situation :-D. But I've seen it happening.