How to locate the Entry Points of a Drupal 8 Core module?
Entry points will equate to routes in Drupal.

Modules will normally define their routes in a YML file named MODULE_NAME.routing.yml, but routes can be defined programmatically as well, check out this article from Acquia about routes: 
 https://dev.acquia.com/blog/coding-drupal-8/defining-and-altering-routes-in-drupal-8/22/03/2016/9891

Also the 'routing' table in the database lists all the paths and their corresponding routes (I believe all).  Note the use of '%' and '{some_value}' to indicate dynamic route values.

Hope that gets you started.