I just want to mention that Nethserver Nextcloud has a custom virtual host function:
http://docs.nethserver.org/en/v7/nextcloud.html#custom-virtual-host
To redirect to Nextcloud instead of showing the default page you may create the file /var/www/html/index.php with following content:
<?php
header ("location: https://yourdomain.com/nextcloud");
?>
Found in this thread.