Symptons same on every release after 16.04.3.

At boot, system hangs on the Ubuntu screen with 4 flashing dots for over 2 minutes.

Ran systemd blame which indicated systemd-networkd-wait-online.service took 1 minute and 38 seconds to run and NetworkManager-wait-online.service took 10 seconds to run.

Ran ubuntu-bug systemd-networkd-wait-online.service which returns that the bug cannot be reported because it concerns a package that is not installed.

Without Apport working, I am unsure how to file the bug on Launchpad.