xsrv VS docker-lemonldap

Yes, OpenLDAP installed from this ansible role

It's dead easy to use TCP/SSL instead of UDP to forward logs. Example rsyslog config

I use rsyslog for that since it's the default in Debian. Configuring forwarding is very simple, a single file in /etc/rsyslog.d/forwarding.conf [1]. Note that this setup uses TLS to encrypt messages so you need to create the relevant certificates (I use self-signed certs). Unencrypted TCP or UDP is simpler, but less secure.

preseed.cfg contains a few basic options needed to setup the OS [1]

I do this with https://github.com/nodiscc/xsrv/tree/master/roles/openldap + https://github.com/nodiscc/xsrv/tree/master/roles/samba. It's just a standalone samba server + LDAP auth for users, no DC or anything like that, so I'm not sure this is what you're looking for.

This ansible role (check the tasks/ directory) gives a good breakdown of what is needed to setup a basic LDAP server and authentication service

I use samba in standalone mode with or without LDAP auth https://github.com/nodiscc/xsrv/tree/master/roles/samba

From what I can see this definitely looks nice. I did find a containerized version here https://github.com/tiredofit/docker-lemonldap

If you want to take it to another level afterwords, you could bolt LLNG onto the stadk and start taking advantage of single sign on (SAML, OIDC, Header based authentication). Fairly light wait, but in production for millions of users....

I have docker images for the following: Fusion Directory - A web based LDAP front end for user/group management OpenLDAP w/FusionDirectory Schemas - The Backend LDAP server that can be communicated to via your applications and also The front end above. LemnonLDAP:NG - Portal of Applications, OIDC, SAML, 2FA (TOTP and Yukikey) and Headers authentication powerhouse. Ties into the above quite nicely along with password resets, password policies, etc.