Comment 4 for bug 1786726

Verification-done with netplan.io 0.40.1~18.04.1:

root@careful-tahr:/run/NetworkManager/system-connections# sudo apt install netplan.io
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following package was automatically installed and is no longer required:
  libfreetype6
Use 'sudo apt autoremove' to remove it.
The following additional packages will be installed:
  python3-netifaces
The following NEW packages will be installed:
  python3-netifaces
The following packages will be upgraded:
  netplan.io
1 upgraded, 1 newly installed, 0 to remove and 37 not upgraded.
Need to get 76.6 kB of archives.
After this operation, 64.5 kB of additional disk space will be used.
Do you want to continue? [Y/n]
Get:1 http://archive.ubuntu.com/ubuntu bionic/main amd64 python3-netifaces amd64 0.10.4-0.1build4 [12.8 kB]
Get:2 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 netplan.io amd64 0.40.1~18.04.1 [63.8 kB]
Fetched 76.6 kB in 0s (164 kB/s)
Selecting previously unselected package python3-netifaces.
(Reading database ... 28984 files and directories currently installed.)
Preparing to unpack .../python3-netifaces_0.10.4-0.1build4_amd64.deb ...
Unpacking python3-netifaces (0.10.4-0.1build4) ...
Preparing to unpack .../netplan.io_0.40.1~18.04.1_amd64.deb ...
Unpacking netplan.io (0.40.1~18.04.1) over (0.36.3) ...
Setting up python3-netifaces (0.10.4-0.1build4) ...
Processing triggers for man-db (2.8.3-2) ...
Setting up netplan.io (0.40.1~18.04.1) ...
root@careful-tahr:/run/NetworkManager/system-connections# sudo netplan apply
root@careful-tahr:/run/NetworkManager/system-connections# ls
netplan-eth0
root@careful-tahr:/run/NetworkManager/system-connections# cat netplan-eth0
[connection]
id=netplan-eth0
type=ethernet
interface-name=eth0

[ethernet]
wake-on-lan=0

[ipv4]
method=link-local

[ipv6]
method=auto
address1=23:b0:87:58:65:f7:fb:8b/45
address2=63:94:73:e1:46:15:79:58/50
dns=2001:4860:4860::8888;
dns-search=cyphermox.net;

I have checked that with an IPv6-only setup, no dns-search is rendered for ipv4 and NetworkManager no longer displays an error message in logs when failing to parse ipv4.dns-search for the 'link-local' method.