My Frankensteined CSS to add a dark theme to the Slack desktop app, based on slack-black-theme.
Navigate to the Slack desktop installation directory:
- Windows:
%localappdata%\slack\
- Linux:
/usr/lib/slack/
- MacOS:
/Applications/Slack.app/Contents/
Open up the most recent version (e.g. app-3.1.1) then open resources\app.asar.unpacked\src\static\index.js and resources\app.asar.unpacked\src\static\ssb-interop.js
At the very bottom of both files, add the contents of loader.js.