Use a third-party CSS or JS Framework, a self-hosted service like a CRM, or a third-party service with the site.
A Drupal 8 port of the Drupal 7 AWS SDK module.
GAnalytics provides flexible Google Analytics integration in Drupal 8 that is easily extensible by other modules.
This module integrates the Who Is Visiting statistics monitoring software into a Drupal site.
The Facebook Instant Articles modules allow administrators to add content from a Drupal site to Facebook, to be viewed on mobile devices as Instant Articles.