Error installing CiviCRM
Following literally the instructions for manual installation as given by David Snopek (https://www.mydropwizard.com/blog/how-install-civicrm-drupal-8-and-why-choose-it-over-pure-drupal-crm) I succeeded in installing civicrm 4.7.27 under Drupal 8.4.2.

One caveat: I installed Drupal with composer (https://www.drupal.org/docs/develop/using-composer/using-composer-to-manage-drupal-site-dependencies), using option B on that page "drupal/drupal" as using this option put vendor under the document root, something that is necessary according to David's blog post. In the Drupal documentation it is indicated that with option B one must manually add some lines to the composer.json file but, at least with 8.4.2, it is all there. But the error code about the libraries folder may indicate that these lines are not available in your composer.json file.

I cannot provide additional help but at least, the instructions from David seem to work still with the latest versions of both Drupal and Civicrm.