This add-on uses network-manager as it's backend. It has a couple issues, at least with the latest Ubuntu. I'll be using it with Raspbian Jessie for the Pi, which should work the same, I think.
The two issues are:
1. The cancel button doesn't work when you goto add a new network. It's a simple fix.
2. The add-on will connect to a network that has already been connected to previously (outside of KODI). When adding a new network, it won't connect though, just accepts the key but does nothing. This was with a WPA network, I haven't tried other encryptions. Those are the main issues I have seen so far. I think it has to be used on Confluence for now as well for the GUI to show up correctly, I haven't looked into that part yet.
The latest developer, but not actively being developed: