Holy crap - that was weird.

Sorry about that @hasu.
After trying
*four micro-USB cables* (including
/two/ that I regularly use to sync data from my Sony Xperia phone), the adapters register with the last cable I tried, which interestingly enough was the
_Logitech K800 recharger cable_ (i.e, not intended for use with data signals, only to charge a wireless keyboard!)
Also tried the Sun adapter: it works perfectly. Nice to be able to use such a "non-PC" keyboard on newer PCs. :-) (I first thought it had the same issue as only Caps Lock, Num Lock, etc. registered with hid_listen. That is until I tried it on the machine directly under X (I monitored hid_listen earlier in a terminal window over ssh). So in short it also works properly with the Logitech cable.
But anyway – on to the topic at hand. This is what is registered
with the Copam K-430 plugged in:
sudo hid_listen
Waiting for device:..........................
Listening:
TMK:e473e8ce/LUFA
USB configured.
Keyboard start.
I174 wFF A1212
ERR:11 ISR:0000 X1713
Obviously I did not expect it to just magically work. Not sure if those error codes mean anything to you. The Num Lock LED and the Caps Lock LED can be toggled (as with the Soarer). No other keys register.
I still haven't obtained an XT board that I could test together with this K-430 to replicate the behavior seen by @latemodel24 (who reported that his K-430 initially output no scancodes with hid_listen
*until an XT board was plugged in*, and the K-430 plugged back, in which case scancodes were seen in hid_listen)
I can do some more testing on this tomorrow, but I am still a little flabbergasted about the micro-USB cable issue (affecting several cables which I know worked on their own, at least against my phone)
