Hi
You would need the LDAPservice User, when using AD. That allows other Apps to query the AD.
See the Account-provider for credentials…
I think what’s missing is a SSL which is accepted by PHP, for example LetsEncrypt.
Even if NethServer has LetsEncrypt, the AD in NethServer uses it’s own self created certs…
What you can do is create a software hook in the LetsEncrypt renewal script, and simply copy these certs to the NSDC folder. These are valid ssl certs, and will be recognized by any App needing SSL from your AD… 
See here:
This works!
Good luck!
My 2 cents
Andy