Comment 3 for bug 1794478

This is not reproducible with netplan in an Ubuntu 18.04 container (on an Ubuntu cosmic host). With the following netplan config:

$ cat /etc/netplan/50-cloud-init.yaml
network:
    version: 2
    ethernets:
        eth0:
            dhcp4: false
    bridges:
      br0:
          interfaces: [eth0]
          dhcp4: true
          addresses: ["fe81::32a5:bc5f:287f:8db8/64"]
$

The container network comes up with:

$ ip addr show dev br0
2: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether da:af:7e:76:48:8a brd ff:ff:ff:ff:ff:ff
    inet 10.141.225.180/24 brd 10.141.225.255 scope global dynamic br0
       valid_lft 3341sec preferred_lft 3341sec
    inet6 fd42:c560:e275:f583:d8af:7eff:fe76:488a/64 scope global dynamic mngtmpaddr noprefixroute
       valid_lft 3340sec preferred_lft 3340sec
    inet6 fe81::32a5:bc5f:287f:8db8/64 scope link
       valid_lft forever preferred_lft forever
    inet6 fe80::d8af:7eff:fe76:488a/64 scope link
       valid_lft forever preferred_lft forever
$

As NetworkManager is not the supported network renderer for Ubuntu Server, please provide a reproducer for this using netplan and systemd-networkd.