tolgaaaltas Did you ever check this? https://discuss.flarum.org/d/17770-friendsofflarum-formatting Idk SoundCloud support but it's supports most of popular services.
pentarou @tolgaaaltas , got an error after activating the extension: Error booting Flarum: Class FoF\Formatting\Listeners\FormatterConfigurator does not exist
tolgaaaltas pentarou you should write this error text on extension page. Developer will help you about this.