Hi Christoph
And Welcome to the NethServer Forum!
If you choose AD as account provider on NethServer, you do get a full AD & LDAP in one.
If using Cockpit, go to Users & Groups:
Use the Bind-DN and Base-DN as shown. ldapservice is the username for anonymous binds like a few apps need.
This module by Stephdl can help you administrate all features of LDAP…
https://wiki.nethserver.org/doku.php?id=phpldapadmin
→ You will need to activate “Kamikaze” mode to allow write access…
If using Web-Apps (eg on another server) you might need to use a valid SSL cert for your account provider - this is NOT the same as your NethServer, which can easily use LetsEncrypt. If you copy over the LE certs, this can also work…
See here:
The next step will make sure that java and other more strict apps can connect to the AD and use it 
In this doc:
My 2 cents
Andy