Your netplan config has enp3s0 as your main interface, and by default that is required for boot, which is why your boot is delayed when you don't have it connected.
Change your netplan 01-netcfg.yaml file to: # This file describes the network interfaces available on your system # For more information, see netplan(5). network: version: 2 renderer: networkd ethernets: enp3s0: dhcp4: yes optional: yes enp0s31f6: dhcp4: yes optional: yes that should start dhcp4 on both your ethernet ports, but also won't delay your boot. See the netplan man page for more details about its config params. ** Changed in: systemd (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1840359 Title: systemd-networkd-wait-online & two ethernet on board To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1840359/+subscriptions -- ubuntu-bugs mailing list email@example.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs