Hi Pete,
Yes,
you are correct, none of the Android versions does support it properly, the way i see it, nobody currently is interested of making a proper Android package for it because the device is not really as good as we could expect.
I have tested the same device PI 3 B+ with IoT and Linux where none really did satisfy me because the problem is the same, the device does simply not have enough kick in it for handling Digital Signage applications.
However,
The chip, the box (which you certainly need), the power adapter and the SD-Card costs are equal with most Android devices that works properly and handles Digital Signage applications pretty well. I have tested Xibo with several Android devices and the result is simply great. Those tested Android devices does cost pretty much same as the PI 3 B+ which means i personally see no reason of wasting my time with PI3 B+
There of course are peoples who does need PI3 B+ for many different uses and purposes where no one can argue about.
Cheers
- dan