This is an extension for Youtube. However, it also affects Youtube Music. In particular, it hides all tracks on any music playlist page. This shouldn't happen.

As an example, take this electro playlist. When I turn off the extension, it correctly shows the tracks in the playlist. But with the extension on, only the playlist thumbnail and the information below it are shown. This is quite annoying, though luckily it doesn't interfere with the actual playback functionality of the site.