I have a wireless bluetooth keyboard (a Logitech diNovo ultra-flat, about seven years old) that I love. Every time I update my Ubuntu installation there’s a ~50% chance that it’ll stop working, and on the update to 15.10 that I just did I got unlucky.

To get it working again I had to comment out the following two lines in /lib/udev/rules.d/97-hid2hci.rules and then reboot.

KERNEL=="hiddev*", ATTRS{idVendor}=="046d", ATTRS{idProduct}=="c70[345abce]|c71[3bc]", \
  RUN+="hid2hci --method=logitech-hid --devpath=%p"

I’ve had to do something similar on more than one previous occasion. The idea originated here, but note that the name of the rules file has changed since that was written.

(When I updated to 15.04 this problem did not manifest. However, I got unlucky and the batteries in the keyboard died while the update was occurring. Batteries in this keyboard typically last 4–5 months, and diagnosing dead batteries is normally easy — hey, the keyboard stopped working suddenly! — but because Ubuntu updates had caused troubles with this keyboard in the past I assumed the update was the cause. I didn’t think to try new batteries until I’d spent a couple of tedious hours deep in the bluetooth configuration weeds. Lesson learned.)

https://blog.mozilla.org/nnethercote/2016/01/09/getting-my-bluetooth-keyboard-working-again-after-an-ubuntu-upgrade/