@Duane Randall: Duane, you’re star. Embedding the required version in the HTML rather than using the XOJO manual recommendation of adding registry entries actually worked.
On the one hand, this seems to solve the Native issue, but I need to look deeper into whether it is viable for us overall - we had hoped to use Webkit across the board of all OS releases rather than be in the [potential] position of having to write / test / support three different Native environments, but at least it is a step in the right direction.
I have nearly finished getting the test project working, so I will still load it later today for interest. I’ll not mark this thread as solved just yet however, as Native was not the way we wanted to go and the Webkit issue is still an problem.