Comment 8 for bug 1743200

+1 I have also stumbled onto this via various searches.

It seems on my host the secondary IP address does get added, but I can't see it anywhere via ifconfig.

cat /etc/netplan/01-default.yaml
network:
  version: 2
  renderer: networkd
  ethernets:
    eth0:
      dhcp4: no
      addresses:
        - 192.168.1.150/24
        - 192.168.2.150/24
      gateway4: 192.168.1.251
      nameservers:
        addresses: [192.168.1.254]

the ifconfig gives me

ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
        inet 192.168.1.150 netmask 255.255.255.0 broadcast 192.168.1.255
        RX packets 205 bytes 18287 (18.2 KB)
        RX errors 0 dropped 42 overruns 0 frame 0
        TX packets 81 bytes 11947 (11.9 KB)
        TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
        device interrupt 20

But doesn't list the second ip address, but "ip address" does.

ip address
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    inet 192.168.1.150/24 brd 192.168.1.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet 192.168.2.150/24 brd 192.168.2.255 scope global eth0
       valid_lft forever preferred_lft forever

it would be ideal if it turned up as a secondary IP address ie eth0:0 or eth0:1 etc..