In Does CiviCRM work with Drupal 8 and how can I help? it mentions https://github.com/civicrm/civicrm-drupal/tree/8.x-master, but from all the other instructions and as best as I can tell https://github.com/civicrm/civicrm-drupal-8 is the correct one to use. What is the difference?
The history of the branches started to diverge around Apr, 2018, and there's a comment on May 1 about creating a separate repo (https://github.com/civicrm/civicrm-drupal/pull/523#issuecomment-385612657):
To facilitate distribution via composer, the Civi-D8 code is being migrated to a new repository with a slightly different branch naming convention (ie firstname.lastname@example.org becomes civicrm-drupal-8@master).
So at the moment for drupal 8 the more current code to use for the drupal module part is at https://github.com/civicrm/civicrm-drupal-8.