Excellent!
This worked for me on my Clara HD, like with this
Cablecc connector, but I got the "left" one, a FBA-U2-241-LE , which results in the connector body covering the Clara power button!
Basically, if you look at the microUSB connector slot on the Clara as shaped like a smile (curved at the bottom), the "left" connector plug has the body to the left, therefore covering the power button of the Clara, though you can kind of squeeze a fingernail underneath to press the button.
Anyway, I followed the instructions above in KOReader terminal, saw in "dmesg | grep sd" (or more correctly, "fdisk -l"), that /dev/sda1 was connected, did a "mount /dev/sda1 /mnt/onboard/shared", and could access the USB key on my /mnt/onboard/shared folder! (Don't forget to "umount" your folder before removing, in case you are not familiar with linux.)
For USB keyboard support on the Clara HD, I did not find that KOReader currently supports it - maybe the recent devices with bluetooth will get it.
In the meantime, with a little elbow grease you can still get USB keyboard support, for example in a
chroot.
* This connector is also handy for plugging a USB keyboard into your phone, so you enter data in your phone, but can mirror the display on your Kobo using
Einkvnc - no external power required, just WiFi.
HOWEVER...Consider the security implications of accessing a secure device (phone that you do banking/email on) from an insecure device i.e. ereader.
If you're more concerned with entering data on the Kobo than viewing the eink display, you can use a variation of this by telnetting or ssh'ing from the phone to the Kobo and entering data on the phone-connected USB keyboard, while using the Vi editor included on the Kobo.
You can install a friendlier editor like nano from
NiLuJe's tools or even installing a small
alpine chroot without the added X for an easier first step.. If you go with the chroot, you may find a script like the one in section 6 of
this comment helpful.
* You may say "Why can't you telnet into the Kobo from the Android and then run Einkvnc on the Kobo to make it mirror the editing that is happening on the Kobo?"
Well you can!
But set ForceWifiOn=true (if you haven't done so already) in your config file [DeveloperSettings] (in KOReader, navigate to .kobo/Kobo/Kobo eReader.conf, Open With Text editor) or else the dropouts may cause frustration.
I have found that none of my Android devices need to be internet-connected to set up as a hotspot so the Kobo can network with my tablet or keyboard-equipped Blackberry Priv with no internet!
And if you are using ConnectBot on Android for telnetting, I think the 1.9.6-oss version and earlier doesn't have the scrolling issue that the later version does.
You can install x11vnc on your xorg chroot, set password with "x11vnc -storepasswd", and run it with "x11vnc -zeroconf", to make sure multivnc android vnc client can discover it.
In fact I am typing this from a USB keyboard connected to an android tablet running multivnc mirroring the Kobo xorg screen.(not being particularly productive).