Possible Regression in handling XML entities

I have XML documents containing HTML entities, e.g. " ".

In Qt5, doc.setContent() accepted these entities, but in 6.1 it does not ("Entity 'nbsp' not declared").

I believe the new behavior is correct because, well, XML isn't HTML, but it's an incompatibility that I have not seen listed or addressed yet in the changes, or how to convert our code from Qt5 to Qt6.

Based on the nature of the problem, I'm assuming is across all platforms.