Two weeks of testing the Demo OpenHAB Server configuration on a Debian powered BeagleBone:

Tons of power-off reboots and all works fine.

Only one time it refused to connect to the outside world.

Stability: 5/5

Security: 5/5

(I finally found the documentation https://github.com/openhab/openhab/wiki/Security + added the Android App + cut the port forwarding)