As described in the documentation regarding docker, you should used the host network for several reasons. Mainly for getting auto discovery to work. If this also applies to the alexa skill, I’m not sure of.
Another solution would be to use macvlan interfaces with docker. The advantage is, that openHAB then appears with an own MAC and IP address on your lokal lan and can do whatever ip communication is necessary.
Yeah I was also thinking on macvlan as an better alternative, but for a quick test maybe go with network host.
But my install getting more and more gritty so before I would screw it up I wanted
make sure that this binding requires it before I start redoing my setup so I don’t do it in vain.