Finally found out how to vanquish the insidious systemd-resolved gremlins in recent Ubuntu-based distros
There's this file "/usr/lib/NetworkManager/conf.d/10-dns-resolved.conf" that you have to shadow with a file of the same name in /etc/NetworkManager/conf.d
So then, in this new file, say you want to use resolvconf again. This is the configuration:
[main]
rc-manager=resolvconf
(dpkg-reconfigure resolvconf and then reboot. resolv.conf should be correct again!)
and yes I have to pin it cause it's almost a year later and I still have to correct this deficiency. May as well make it easier for me to find.
@yakkoj that's why I run Devuan where I can when I am working with Debian-based systems.
The system shipped with this configuration, which forces systemd-resolved:
[main]
dns=systemd-resolved
You're overriding all of this when you shadow the file.
Also, don't forget:
systemctl mask systemd-resolved && systemctl disable systemd-resolved
(oops, typos)