As *BSD defaults to use IPv6 only sockets and Linux to IPv4 mapped IPv6
sockets, switches to support explicit binding address families are required.
Now set explicitly if you want IPv6 only, IPv4 only or mapped IPv4.
Caveat:
OpenBSD explicitly states to not support IPv4 mapped IPv6 via setsock-API
Assuming an /opt/ install. For those unfamiliar, plop it into /etc/systemd/system (symlinks might not work, old systemd bug), run `systemctl daemon-reload`, and have it start on boot (and immediately) with `systemctl enable --now endlessh.service`
