USB devices connected through a hub are not seen by the kernel on birch device

I've tried to connect both a j5 Create JCA374 and Startech HB30C3AGEPD hub. One end of the thick type-C to type-C cable is plugged into the wall wart and the other end is plugged into the hub's power port. The hub's cable is plugged into the type-C socket on the birch device.

In both cases, the battery icon in the status bar in phosh changes to the charging icon. However, no devices connected to the hub's ports are seen by the kernel. On the j5 Create hub, a mouse plugged in does not get powered up. On the Startech hub, the mouse is powered up (lights come on) but nothing is seen by the kernel. Devices on my KVM switch are not seen. None of the on-board devices in either hub, in particular the Ethernet NIC (the motivation for getting the USB port working), are seen by the kernel.

This is very similar to the behaviour described in linux-emcraft#41.