HOWTO: do not wait for network to be online at boot
By default, systemd-networkd waits for the network to be online before continuing boot, using the systemd-networkd-wait-online.service.
This is useful, for example, for servers, or systems that rely on networked file systems, but it might not be the best default for a personal laptop, or a media player.
To disable this feature, disable or mask systemd-networkd-wait-online:
systemctl disable systemd-networkd-wait-online.service