Latest firmware can be found here: link
I was having problems with it not willing to update and was getting failed updates:
Reboot device /dev/serial/by-id/usb-0658_0200_12345678-9012-3456-7890-123456789012-if00 (ConBee II)
slip put 0xC0
slip put 0x81
slip put 0x02
slip put 0x7D
slip put 0xFF
slip put 0xC0
retry, failed
2410: Error: uart reset failed, check retry
Flashing Error! Please re-run this script...
searching a bit further i found how to give docker access to the USB device (don't forget to change the xxxxx part to something that makes sense for you):
docker run -it --rm --entrypoint "/firmware-update.sh" --privileged --cap-add=ALL -v /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DExxxxxxx-if00:/dev/ttyACM0 -v /lib/modules:/lib/modules -v /sys:/sys deconzcommunity/deconz
Now the update was a SUCCESS :) after this you can:
docker rmi deconzcommunity/deconz
and don't forget to reboot home assistant
most of this was pieced together via community.home-assistant.io