https://thenextweb.com/apps/2019/03/12/how-to-turn-on-slacks-dark-mode-on-ios-and-android/

Slack‘s finally rolling out its dark mode on its iOS and Android apps. We’ll show you how to turn on the dark mode, but first make sure that you’ve got the latest version of the app.

— Slack (@SlackHQ) March 11, 2019