For reference, it appears that a systemd unit file has been shipped since 1.3.17 due to <https://github.com/xelerance/xl2tpd/pull/226>. Unfortunately, it is not currently installed because dh_installsystemd is not called by debian/rules, as described in <https://github.com/xelerance/xl2tpd/pull/264>.
Cheers, Kevin
