my setup
Unfortunately, I don't have such a device, but are you sure this USB Y-cable with OTG-adapter is suitable for this purpose?
Maybe the middle two USB wires (DATA+/DATA-) are not shared in this Y-splitter (or I don't know, what is this), so I think this will not work.
I think the tuner only gets the power and that's it.
You should try adding a dedicated power supply to the 2nd micro USB port (I mean a real power supply, not a phone charger) and connecting the tuner to the first via OTG.