Digging even further back, it turns out that IFDOWN is in itself a workaround for an equal issue dating back to ~2012. As such, the core of the issue lies with how initramfs network setup overrides netplan. Adding that package.
Given the very limited setup /etc/initramfs-tools/initramfs.conf allows (including the DHCP default mentioned in the description), there is a case to be made for allowing admins to rely on the full config rather than initramfs for their network setup. ** Also affects: initramfs-tools (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1813394 Title: DROPBEAR_IFDOWN=* takes interface down but leaves netplan config To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/dropbear/+bug/1813394/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs