As of today GIT sources, 5.6 branch, deferred rendering examples are broken. Both cpp and qml.
Since 5.6.0 beta is nearing, I would say this is a blocker issue, unless you really want to deploy broken examples.

I am aware there is an ongoing activity in the lights area, but I am kind of disappointed that the deferred rendering technique is always the first that gets broken.
It seems to me that it is condidered like a second class technique as there is not much interest in progressing and fixing it.
See an almost 6 months old issue that is still not fixed: https://bugreports.qt.io/browse/QTBUG-46707