I have installed the Joomla appliance VM and everyhting works well.
However, we need to make Joomla a Service Provider (SP) in a SAML federation so that the SAML Identity Provider (IdP) can authenticate users and re-direct them to Joomla in Single-Sign-On
This scenario has worked well with a regular Ubuntu VM, with a Joomla 1.5 package and the SAML plugin in Joomla.
What is happening in the Joomla appliance, I believe, it's the way Joomla is installed as a Virtual Host. When we install the SAML plugin in Joomla, the metadata created by the SAML plugin in the Joomla appliance is of the form: