Comment 10 for bug 1817655

Verification-done for bionic:

Changing the renderer to NetworkManager still leads to a working system with live connections, even with the NetworkManager files now having a .nmconnection extension:

ubuntu@just-boa:~$ dpkg -l netplan.io | grep ii
ii netplan.io 0.96-0ubuntu0.18.04.2 amd64 YAML network configuration abstraction for various backends
ubuntu@just-boa:~$ networkctl
IDX LINK TYPE OPERATIONAL SETUP
  1 lo loopback carrier unmanaged
  2 enp2s1 ether routable unmanaged
  3 enp2s2 ether degraded unmanaged

3 links listed.
ubuntu@just-boa:~$ nmcli
enp2s1: connected to netplan-enp2s1
        "Realtek RTL-8100/8101L/8139 PCI Fast Ethernet Adapter (QEMU Virtual Machine)"
        ethernet (8139cp), 52:54:00:BC:B0:18, hw, mtu 1500
        ip4 default, ip6 default
        inet4 10.3.21.29/20
        route4 10.3.16.0/20
        route4 0.0.0.0/0
        inet6 2001:470:b171::5/48
        inet6 fe80::5054:ff:febc:b018/64
        route6 ff00::/8
        route6 2001:470:b171::/48
        route6 fe80::/64
        route6 ::/0

enp2s2: connected to netplan-enp2s2
        "Realtek RTL-8100/8101L/8139 PCI Fast Ethernet Adapter (QEMU Virtual Machine)"
        ethernet (8139cp), 52:54:00:59:A3:52, hw, mtu 1500
        inet4 169.254.41.37/16
        route4 224.0.0.0/4
        route4 169.254.0.0/16
        inet6 fe80::5054:ff:fe59:a352/64
        route6 ff00::/8
        route6 fe80::/64

lo: unmanaged
        "lo"
        loopback (unknown), 00:00:00:00:00:00, sw, mtu 65536

DNS configuration:
        servers: 10.3.21.25 149.56.20.136
        interface: enp2s1

Use "nmcli device show" to get complete information about known devices and
"nmcli connection show" to get an overview on active connection profiles.

Consult nmcli(1) and nmcli-examples(5) manual pages for complete usage details.
ubuntu@just-boa:~$ sudo ls -l /run/NetworkManager/system-connections/
total 8
-rw------- 1 root root 353 Apr 2 16:18 netplan-enp2s1.nmconnection
-rw------- 1 root root 168 Apr 2 16:18 netplan-enp2s2.nmconnection