Comment 7 for bug 1869181

Something related to NetworkManager is preventing systemd-networkd from starting.

networkd-dispatcher[1163]: WARNING: systemd-networkd is not running, output will be incomplete.

Normally after network-pre.target, systemd-networkd-wait-online.service runs
and blocks until systemd-networkd has brough up configured interfaces.
systemd-networkd did not start so when cloud-init.service runs network is
*not* up like it expects.

systemd[1]: Finished Initial cloud-init job (pre-networking).
systemd[1]: Reached target Network (Pre).
systemd[1]: Starting Initial cloud-init job (metadata service crawler)...
cloud-init[931]: Cloud-init v. 20.1-10-g71af48df-0ubuntu2 running 'init' at Wed, 08 Apr 2020 05:45:26 +0000. Up 31.04 seconds.
cloud-init[931]: ci-info: +++++++++++++++++++++++++++++Net device info+++++++++++++++++++++++++++++
cloud-init[931]: ci-info: +-----------+-------+-----------+-----------+-------+-------------------+
cloud-init[931]: ci-info: | Device | Up | Address | Mask | Scope | Hw-Address |
cloud-init[931]: ci-info: +-----------+-------+-----------+-----------+-------+-------------------+
cloud-init[931]: ci-info: | enp2s0 | False | . | . | . | 6c:2b:59:59:9d:ca |

Notice later, NetworkManager takes over the ethernet device:

kernel: r8169 0000:02:00.0 enp2s0: Link is Up - 1Gbps/Full - flow control rx/tx
kernel: IPv6: ADDRCONF(NETDEV_CHANGE): enp2s0: link becomes ready
NetworkManager[1035]: <info> [1586324867.0369] device (enp2s0): carrier: link connected
NetworkManager[1035]: <info> [1586324867.0380] device (enp2s0): state change: unavailable -> disconnected (reason 'carrier-changed', sys-iface-state: 'managed')
NetworkManager[1035]: <info> [1586324867.0403] policy: auto-activating connection 'netplan-enp2s0' (7ea6f90b-3495-3533-948a-ef0035687c34)
NetworkManager[1035]: <info> [1586324867.0425] device (enp2s0): Activation: starting connection 'netplan-enp2s0' (7ea6f90b-3495-3533-948a-ef0035687c34)
NetworkManager[1035]: <info> [1586324867.0430] device (enp2s0): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'managed')
NetworkManager[1035]: <info> [1586324867.0445] manager: NetworkManager state is now CONNECTING
NetworkManager[1035]: <info> [1586324867.0454] device (enp2s0): state change: prepare -> config (reason 'none', sys-iface-state: 'managed')
NetworkManager[1035]: <info> [1586324867.0470] device (enp2s0): state change: config -> ip-config (reason 'none', sys-iface-state: 'managed')
avahi-daemon[1011]: Joining mDNS multicast group on interface enp2s0.IPv4 with address 192.168.101.86.

The network config maas sends is for Ubuntu Server, which defaults ethernet
devices to be controlled by systemd-networkd; I suspect Desktop has a
different policy in place which puts all network devices in NetworkManager
control, so this config that MAAS sends (also, this MAAS looks old, it's
sending network config v1 (not v2, netplan)).

network:
    config:
    - id: enp2s0
        mac_address: 6c:2b:59:59:9d:ca
        mtu: 1500
        name: enp2s0
        subnets:
        - address: 192.168.101.86/24
            dns_nameservers:
            - 192.168.101.1
            dns_search:
            - maas
            gateway: 192.168.101.1
            routes:
            - destination: 10.101.46.0/24
                gateway: 192.168.101.1
                metric: 200
            type: static
        type: physical
    - address:
        - 192.168.101.1
        search:
        - maas
        type: nameserver
    version: 1

On Focal desktops, this file is now present:

% cat /etc/netplan/01-network-manager-all.yaml
# Let NetworkManager manage all devices on this system
network:
  version: 2
  renderer: NetworkManager

You will need to use a script/preseed to modify this value to
be networkd like this:

network:
  version: 2
  renderer: networkd