Thanks.
The installation manual (v1.03) for the straight antenna has a section about it (the installation manual (v1.02) for the elbow antenna does not, strangely):
Here's the full text from the images:
"The USB port that you connected the JST cable to internally can no longer be used by a USB device.
Plug the USB hole plug into the USB jack of the Pi3 or Pi4 used for the internal connection of the JST cable.
On the Pi3, this will be the top jack of the left column as shown in the photo.
For the Pi4, this is the also the top jack of the left column (the black colored jacks, not the blue ones).
Make sure you orient the plug correctly. The part of the plug that engages the jack is offset so that the cover portion of the jack does not interfere with a USB device plugged into the jack below it."
