If you have a Debian or Ubuntu system available, installing the `slapd` package (OpenLDAP) would be sufficient to get something on localhost or ldapi:///. RH-based systems have openldap* packages.

You don't really have to do much more than that for the purpose of testing this (no creating of accounts, groups, sub-trees, etc).

Perhaps at most go to the stanza/paragraph that defines "olcDbIndex" values, add a new one, and see if a new index file is created in "olcDbDirectory" (often /var/lib/ldap):

* https://www.zytrax.com/books/ldap/apa/indeces.html

* https://warlord0blog.wordpress.com/2020/10/19/ldap-indexes/