It does sound like it would be best for a fixed setup. The only unknown for me is whether Android that lacks 3.5mm port could handle USB to HDMI and TRRS to USB at the same time.
I just tried it out with headphones (Phone > HDMI/USB Hub > USB A to C adapter > google usb c to 3.5mm adapter) and it seems to work.
It would be interesting to test it with the $<5 USB sound cards but I don't have one on hand.
It does sound like it would be best for a fixed setup. The only unknown for me is whether Android that lacks 3.5mm port could handle USB to HDMI and TRRS to USB at the same time.