Drupal 8 runs on all of our hosting packages. To install Drupal 8 on CiviHosting:

composer create-project drupal-composer/drupal-project:8.x-dev some-dir --no-interaction

where you can replace some-dir with whatever directory you want. If you are in /www/www/ then you could use just a dot: ..

Now you can use Drush from the command line — it is already installed on all of our servers. 🙂