Problem is the Xiaomi Gateway. (no reply from support there after 3 weeks)
Even with the Mi Cubes, it only sends gestures and not what face is up.
I ditched the Xiaomi Gateway and went the ConBee/deConz route instead.
Have a read about it:
here (Mi cube posibilities)
here (Aqara support as of 12. june -18)
and here (for OH2 integration)
Yes, it’s another USB dongle, but makes the cubes much more useful. 
As far as I can tell, the OH2 Zigbee binding does not support the ConBee, and with the Ti dongle it does support, does not support the cubes. (correct me if I’m wrong)
On Linux, the deConz (free) SW is easy to set up running headless under systemd.
Even with the 500ms localhost polling of the whole /sensors section from REST, it only uses 2-3% CPU.