Comment 1 for bug 1713226

Is this on upgrades to artful? or clean-install / clean-bring up of artful?

Note that artful will no longer have ifupdown installed on clean-install, and thus /etc/network/interfaces changes for clean-installs will have no effect at all. And one should instead use netplan e.g. $ sudo netplan ifupdown-migrate
to move the system over to networkd.

The router advertisement vs networkmanager is interesting case. In practice networkd should not have configured the interface imho, if it was not told to manage it via netplan configuration. Or e.g. NetworkManager should still consider interface for management, even if it has acquired RA ipv6.