This also happened to me with the latest update, my server (Dell Poweredge T420) stalled on boot up with the message etho 0 not connected, and something about IPv4 address: not set, IPv6 address: not set. leading to no ip address could be found.
i tried everything from this forum, www, to sort this and was pulling my hair out to sort this to no avail, then i remembered i had a recent - ish flash back up, and reverted back to that, it was not that simple as i had changed a few things in the last week tidying up files etc, and what a palaver that was getting things back to a working system.
Anyway i backed up the previous version that works for me until this is rectified, so remember always back up before upgrade is a lesson to me.
PS:- i usually do back up before update, but the updates have been going so well without issues i thought just do it 🙂 how wrong was i .....