The USB keyboard should have worked. Historically there was a bug that caused the USB hub to not reset and detect things but that claims to have been fixed in the upstream kernel some time (a couple of years) ago.
HDMI-CEC should also work, although this is something I never normally test because I have too many CEC capable devices attached to the same AVR and it causes problems; so I disable/block it on the AVR.
If you add ssh to the boot params in exlinux.conf the SSH daemon is forced to start on boot, and then you can SSH in to the device and use kodi-remote to navigate the screen same as a remote control. The Odroid remote is also supported OOB if you have one.