How to set up DNS on Ubuntu 22.04 without a netplan config.

I finally found the solution here: https://serverok.in/systemd-resolved ( Archive.org cache)

In case the link dies in the future, Create a file:

sudo mkdir /etc/systemd/resolved.conf.d/
sudo nano /etc/systemd/resolved.conf.d/dns_servers.conf

Add my DNS in this file:

[Resolve]
DNS=8.8.8.8 1.1.1.1

Then restart systemd-resolved

sudo systemctl restart systemd-resolved

It works even after reboot :-)

PS : No idea why my DNS configuration was lost during the upgrade from 20.04 to 22.04.