@Wong
I ran the USB Host Diagnostics app. I wasn't running as root. I was using a cheap OTG cable with a USB key. I haven't tried on any other device, so I can't confirm that the OTG cable actually works. Anyway my results were:
Code:
Build ID: 2016-04-27_16-24_dev_586b734
Android API:
Claims support: Yes
Classes found: Yes
Device detected: No
Rooted API:
Claims support: No
Device detected: N/A
Kernel:
Claims support: Yes
Device detected: No
Verdict:
OS support: No
3rd party apps: No
I don't know where you go from here.
I'm happy running my Logitech K480 Bluetooth keyboard anyway. I used it to type for about 4 hours a few days ago, all working fine, and the Android shortcut keys on it are fairly useful.