drupal site:install \
--learning \
--uri="http://testing.site" \
--langcode="en" \
--db-type="mysql" \
--db-host="localhost" \
--db-name="drupal8_site" \
--db-user="somesiteuser" \
--db-pass="really secure password" \
--db-prefix="prefix_" \
--db-port="3306" \
--site-name="Drupal 8" \
--site-mail="admin@example.com" \
--account-name="anything but admin" \
--account-mail="admin@example.com" \
--account-pass="another really secure password" \
minimal # the profile name
option is needed when dealing with multi-site.