The documentation has some mistakes and is incomplete... That's why you don't have a
/etc/slapd directory. We've started to talk about that here, it's in progress, if you want to join, try, contribute... You're welcome!
The admin password is never changed from the YunoHost code - at least not deliberately, we're not insulated from a bug somewhere.
Just a regular LDAP server using OpenLDAP, from where all the users are stored - even the admin one.
Note that we use the
/etc/ldap/slapd.conf file at first to generate the
/etc/ldap/slapd.d which is then used by the LDAP database to provide the configuration. So, if you modify
slapd.conf, it will only take effect after regenerated the
slapd.d directory. Alternatively, you can change this behavior by modifying the file
/etc/default/slapd - I think it's related to
SLAPD_CONF= - or try to remove the
slapd.d directory before restarting slapd...