@julio Forgive me since my French is not 100%, but what I read is you want to deploy a target computer that is either debian or ubuntu. You want to connect to an LDAP service to allow users to log onto the linux computers with a single password. You say that windows AD is to complicated.
I think since you have windows AD already setup that is the best choice for you instead of setting up openldap and have a second authentication database. You say that connecting to AD is a problem. What stops you from connecting to AD? Is there a technical reason? Or just too many steps to connect to AD?
What I think could happen is that you deploy a linux computer to a target computer, then run a FOG snapin that connects the target computer to windows AD using a script. I did a quick google search and I do find examples of scripts that do what you want. https://github.com/Makubo/linux-ad-join is one example.
If you setup openldap, you will still need to script the target computer so that it connects to your openldap server. So the amount of work is the same. If the people that will use these linux computers also use microsoft windows, then windows AD is the best choice.