Comment 4 for bug 1451232

Thanks - could you please try

sudo systemctl stop lxc-net
sudo systemctl start lxc-net

then see whether 'ps -ef | grep lxcbr0' shows a result? If it does
not, repeat up to two more times (and then just give up and let us know :)

If lxcbr0 does show up, does the container (with its original config)
come up fine?

I've had this issue too - the lxc-net systemd job appears to not be
correct, or it interacts badly with network-manager. It doesn't just
not show up, it also disappears quite often.