UIInput.current
We tried that, but it wasn't working for some reason.
We opted to filter for UICamera.selectedObject and that seems to be working.
Though of course, we can't use switch on type GameObject (which both .selectedObject & .current are), so we're now using a series of if statements

Also, is there a reason that OnInputChanged message doesn't go through the eventReceiver and/or is not forwarded with UIForwardEvents?
Any word on the discrepancy here?