This is a work in progress module for drupal 8.
It allows to create multiple shoutboxes, and provide a block to see it.
Via composer
composer require kgaut/shoutbox
Through the UI : /admin/module
or via drush : drush en shoutbox
Through the UI : /admin/people/permissions
Through the UI : /admin/content/shoutbox
You can access it via /shoutbox/ID eg : /shoutbox/1.
You can also place a block and select the shoutbox you want to display