To make LDAP on port 389 accessible from the LAN it is necessary to edit /etc/default/slapd
as follows, replacing 127.0.0.1 with 0.0.0.0:
# SLAPD_SERVICES="ldap://127.0.0.1:389/ ldaps:/// ldapi:///"
SLAPD_SERVICES="ldap://0.0.0.0:389/ ldapi://%2fvar%2frun%2fslapd%2fldapi/????x-mod=0777"
Note that you can add the individual IP address(es) instead of 0.0.0.0 (listen all), but it is probably better to control access through a firewall.