OK - bummer. Looks like you covered everything from that aspect. I’m not sure developer options will help at all in this case.
Just to be clear you did try this combo right (red ticks) - I know you said both controlled by were selected and you couldn’t change)? But could you do file transfer, or did you mean from your comment that wasn’t available (grayed out)?
One other thing I know from personal experience, and from working in IT in the past, is that those little USB hubs are often highly erratic in how they perform. Especially if they don’t have their own built in power - just because its worked okay with other devices doesn’t mean its 100% reliable…
So it might not be the phone - do you have any alternative hubs to try - especially a laptop one or similar with its own power supply?