For anybody still looking for such a solution here's my contribution:

Mac Mini server 2010 running 10.13 + Hideez Smart USB Bluetooth-adapter works perfectly with Flic 2 (I use the button in universal mode to zoom and close windows since I use the mini as my media center).
It won't work with 10.12. The button pairs at first, but looses connection after a few seconds and does not execute any of the universal commands. 10.13 solved the problem!

Just make sure you follow these instructions: https://dongle.hideez.com/how-to-use-hideez-bluetooth-dongle-on-macos

Especially the terminal line so that it always uses the dongle and not the internal BT module.

Ver satisfied indeed!