Your OpenLDAP configuration will be compatible between 2.4.23 and 2.4.33. But LTB project install OpenLDAP in /usr/local, not in the default location, so you need to move your configuration in the new location.
Please continue this thread on LTB mailing lists if you need specific information on these packages :
http://ltb-project.org/wiki/community#mailing_lists
Clément.