I'm in a situation where it's very important I know immediately if someone speaks in a particular Slack channel. I need my phone to beep when someone speaks in this Slack channel.

My Android phone has Slack installed.
My phone's in DND, but Slack is set as a DND exception (all notifications).
Slack has all notifications enabled.
I go into Slack. I enter the channel. I tap the name at the top, click "Settings & details". It says "Notifications: All new posts".

So why is my phone not beeping?

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