A tiny Discord css-injector.
git clone https://github.com/mlvzk/discocss
cp discocss/discocss /usr/bin # or any other directory in your $PATHPut your css in ~/.config/discocss/custom.css
Run discocss
If after an update your theme doesn't work anymore, close and run discocss again. Discord might be running in the background without you knowing, so if it still doesn't work, use pkill.