Even easier dark mode for Slack - h/t https://dev.to/changoman/easy-dark-mode-for-slack-1mmn

slackdarkmode.sh

#! /usr/bin/env bash

# install:
# wget https://gist.githubusercontent.com/vaxinate/2d85f54ae6d279531f45bb8ec5dcd1a8/raw/1b89b34bdedea60394c445e97688d90924022af6/slackdarkmode.sh
# sudo cp slackdarkmode.sh /usr/bin/fixslack
# usage:
# fixslack

fixslack(){
  FILEPATH=/Applications/Slack.app/Contents/Resources/app.asar.unpacked/src/static/ssb-interop.js

  SLACKDARKMODE='//slack darkmode
  document.addEventListener("DOMContentLoaded", function darkMode() {
    $.ajax({
      url:
        "https://cdn.jsdelivr.net/gh/laCour/slack-night-mode/css/raw/black.css",
      success: function success(css) {
        let overrides =`
          code, pre { background-color: #535353; color: #85c5ff; }
          .c-mrkdwn__pre, .c-mrkdwn__quote, pre { background: #535353 !important; background-color: #535353 !important; }
          #client_body:not(.onboarding):not(.feature_global_nav_layout):before {display: none;}
        `
        $("<style></style>")
          .appendTo("head")
          .html(css + overrides)
      },
    })
  })'

  echo "enabling dark mode... You'll need to enter your password."
  (! grep -q '//slack darkmode' $FILEPATH) && echo "$SLACKDARKMODE" | sudo tee -a $FILEPATH > /dev/null
  echo "restarting Slack..."
  killall Slack && open /Applications/Slack.app
  echo "fixed!"
}

fixslack