You just created an Ubuntu container (release=xenial, arch=amd64, variant=default)

To enable sshd, run: apt-get install openssh-server

For security reason, container images ship without user accounts
and without a root password.

Use lxc-attach or chroot directly into the rootfs to set a root password
or create user accounts.
Configuring the Unity8 LXC...
Starting the container
usage: unity8-lxc-setup [-h] [--rebuild] [--test SECONDS] [--destroy]
                        [--update-lxc]
unity8-lxc-setup: error: Unable to start the container.