I thought it might have been the cable so I tried an external MHL adapter and ended up with the same result. Then I hooked up some other android devices(tronsmart prometheus, and an ouya (running CM11)) through hdmi with USB attached and again received the same response. It does however work normally with every variety of x86 computer I've tried; even android x86.
This seems very similar to a configuration issue I fixed on an a touchscreen Ubuntu laptop years ago. Some googling helped me solve that one quickly and easily, but the problem is that I have no idea where to start on this one. Searching is almost impossible as any combination of "android" and "touch screen" tends to take me off in the wrong direction. Even here 4 out of the 5 threads I've found are at least 5 years old and quite hypothetical.
Of course it could always be a deeper issue involving a lack of kernel support, in which case I'm probably screwed.
Any suggestions on where/how to start? If nothing else this can at least act as a warning for people not to buy MHL HDMI touchscreens and expect them to work with android phones out of the box. At least not yet.
Thanks for any ideas in advance