If you would like to use Ubuntu Linux distribution in your AppVMs, you can build and install one of the available Ubuntu templates. These templates are currently not available in ready to use binary packages, because Canonical does not allow redistribution of a modified Ubuntu. The redistribution is not allowed by their Intellectual property rights policy.
To quickly prepare the builder configuration, you can use the
available in the repository - it will interactively ask you which templates you
want to build.
The build for Ubuntu 14.04 LTS (Trusty) should be straightforward.
The build for Ubuntu 16.04 LTS (Xenial) is straightforward. Note that packages perl-Digest-MD5 and perl-Digest-SHA are required for the build to succeed.
If you want to help in improving the template, feel free to contribute.