Only works on Minecraft 1.8.9 with Forge 11.15.1.2318.

Had to downgrade use IntelliJ 2019.3.5 with a JDK 8 for Gradle to work.

Download it: https://github.com/Minikloon/KloonMute/releases

For latest version see: https://github.com/Minikloon/KloonMuteLatest