I was surprised to find that the Hardkernel USB bluetooth adapter was not recognized in CoreELEC 184.108.40.206 on my Odroid C2 - it does not show up at all in the Bluetooth settings.
Upon further investigation, it seems that this device is a Broadcom BCM2045 controller (id 0a5c:2045) which has problems with the stored link key commands failing when the device is brought up.
I’ve confirmed that backporting this patch from the btusb driver fixes the bug and the device appears to be working fine: https://www.spinics.net/lists/linux-bluetooth/msg64780.html
Happy to provide a PR if that helps.
This shouldn’t be an issue for any devices that can use the amlogic-ng kernel, as that one already includes this patch.