The coloured wires with shrinkwrap are usb wires with the tiny usb to serial adapters connected inline.
The white port in the background is an otg adapter.
This is the smaller setup of the 2. With a small usb hub wired inline. It works correctly on another computer.
This is with a powered usb hub as well as the inline hub to ensure that everything has enough power. Same result.
This is a usb cable wired straight to the usb to serial adapter. This works correctly.
The same wire with the hub, does not work.
I think it must be something to do with the way that the apm interfaces with the usb devices via any hub, because linux sees them correctly:
This is using a script that lists usb devices and the /dev/ entry that matches them.
And, in case it makes any difference, my apm.sh:
Apologies for using my phone to take pictures!
Thanks for your help!