Comment 12 for bug 1881832

Installed 20.04LTS Desktop on Hyper-V, after install there is no network connectivity, host network is ipv4 only network with dhcp, no other VM (or physical) has any issues. This is how it is immediately after install and updates.

/etc/netplan/01-network-manager-all.yaml only constains 3 lines:

network:
  version: 2
  renderer: NetworkManager

Nothing else. After manually adding:
  ethernets:
    eth0:
      addresses: [ 192.168.0.20/24 ]
      gateway4: 192.168.0.1
      nameservers:
        addresses: [192.168.0.1, 1.1.1.1, 1.0.0.1]

there is connectivity. But now DNS doesn't work (plenty of topics this around internet without a definite resolution), quick fix is to:

sudo echo nameserver 192.168.0.1 > /etc/resolv.conf

unfortunately i've no idea of a more permanent fix, this must be done after every boot.