Directadmin doesn’t have possibility to add SSL certificate for a subdomain, unless You add it as a separate domain in domain control.

You may also use separate SSL certificates by creating a custom httpd (or nginx, but it would require to change the CAROOT line) file in user configuration dir i.e. loginroot.com.cust_httpd (or loginroot.com.cust_nginx if it’s nginx).

|*if SUB="subdomain"|
	|?KEY=/usr/local/directadmin/data/users/loginroot/domains/subdomain.loginroot.com.key|
	|?CERT=/usr/local/directadmin/data/users/loginroot/domains/subdomain.loginroot.com.cert|
	|?CAROOT=SSLCACertificateFile /usr/local/directadmin/data/users/loginroot/domains/subdomain.loginroot.com.cacert|
|*endif|