As mentioned in the documentation, it is possible to manage ckeditor plugins using composer : https://www.drupal.org/docs/8/core/modules/ckeditor/managing-ckeditor-pl... →
It would be interesting to set this up in this module to avoid any manual download and installation of javascript librairies.
Not all content is available!
It's likely this issue predates Contrib.social: some issue and comment data are missing.