Not really a nethserver feature, but something I found out during Nextcloud migration: the ns8-migration app disables nextcloud and puts a redirection webpage in place.
I added a .htaccess file with a permanent redirect. The nextcloud desktop client (latest versions) will change the nextcloud URL accordingly. Nice feature.
Android / IOS clients give a user warning, and need to be reconfigured manually.
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{HTTPS} on
RewriteCond %{REQUEST_URI} ^/nextcloud(/.*)?$ [NC]
RewriteRule ^ https://[new nextcloud URL]/ [R=301,L]
</IfModule>