Does NADI work on SiteGround?
Yes. When using SiteGround's VPS instances hosted with cPanel you have to get in contact with their admin team. SiteGround has php_ldap compiled to lookup the LDAP configuration at /etc/openldap/ldap.conf. Neither the directory nor the file does exist. Let the support team create both with write permissions for your SSH user.
Copy your domain controller's PEM file to /etc/openldap/dc.pem
Paste the following content into /etc/openldap/ldap.conf
TLS_REQCERT never TLS_CACERT /etc/openldap/dc.pem