I've figured out how to work around this. It's all documented at http://djanotes.blogspot.com/2018/04/anonymous-bridges-in-netplan.html.
In short, I tell systemd-networkd directly to bring up the bridge. To do this, in addition to the rest of the configuration in netplan, I create /etc/systemd/network/br0.network with the following: [Match] Name=br0 [Network] LinkLocalAddressing=no IPv6AcceptRA=no This leads to the interface being brought up and not getting an IPv4 or IPv6 address. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1736975 Title: netplan does not bring up anonymous bridge on boot To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/nplan/+bug/1736975/+subscriptions -- ubuntu-bugs mailing list firstname.lastname@example.org https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs