nspawn: fallback to host network mode if networkd is not running
nspawn: fallback to host network mode if networkd is not running

On Debian systemd-networkd is not the default network manager, so
there's nothing configuring the veth bridge.
If networkd is not running, simply fallback to using the host
network. This will not provide isolation, but at least the
connectivity is restored.

systemd/mkosi,systemd/mkosi