[Resolve]
DNS=<%= node[:networking][:nameservers].join(" ") %>
Domains=<%= node[:networking][:search].join(" ") %>
DNSSEC=allow-downgrade

[Resolve]
DNS=<%= node[:networking][:nameservers].join(" ") %>
FallbackDNS=1.1.1.1 9.9.9.10 8.8.8.8 2606:4700:4700::1111 2620:fe::10 2001:4860:4860::8888
Domains=<%= node[:networking][:search].join(" ") %>
DNSSEC=allow-downgrade

Add a systemd-resolved FallbackDNS list
Add a systemd-resolved FallbackDNS list

The default in systemd for ubuntu in 18.04 is an empty fallback
list.

Use a reasonable list:

* Cloudflare (https://1.1.1.1/)
* Quad9 without filtering (https://www.quad9.net/)
* Google (https://developers.google.com/speed/public-dns/)
1.1.1.1
9.9.9.10
8.8.8.8
2606:4700:4700::1111
2620:fe::10
2001:4860:4860::8888

List from https://git.archlinux.org/svntogit/packages.git/tree/trunk/PKGBUILD?h=packages/systemd#n103
