Inbound = something that requires a response/action. Could be an automated alert that creates a ticket, could be a slack message from someone asking for something.

If you're not great with it every message can feel like an inbound and you're compelled to go cycle through all the channels and read everything whether it's immediately relevant or not.

I think the meaning of inbound here refers to work that is defined or asked of you or a team via Slack instead of via more thought-out and defined work.

I mean sources of incoming work, could be a quick question, an ask for something, automated alarm or a bug.

Slack makes it super hard to stay on top of this and systematically triage the low from the high value.