Comment # 2 on bug 956159 from Marius Tomaschewski

Ah... yes.

The ldap service name changed from ldap.service to slapd.service and
slapd.service does not provide any alias.

sed -e "s/ldap.service/slapd.service/g" \
    < /usr/lib/systemd/system/dhcpd.service > /etc/systemd/system/dhcpd.service
sed -e "s/ldap.service/slapd.service/g" \
    < /usr/lib/systemd/system/dhcpd6.service >
/etc/systemd/system/dhcpd6.service

And yes, there is no ldap support in the dhcpd6 daemon on 13.2 at all.