Nextcloud Security Scan (host_prefix hardening feature not enabled)

When I run my cloud server against nextcloud’s security scan, it reports that a server hardening feature is not enabled. Specifically, it reports a problem with “_host-prefix.” I believe this is why my server only receives an A rating instead of an A+ rating. I currently access my cloud server at From what I have been able to discover, the server should be addressable as without any subfolders. If I try to access my server in this manner, the site is not found. Is it possible to setup the Nextcloud portion of Mailinabox, to be addressed without subfolders?