Livestreamer is currently not being maintained, but a fork called streamlink exists.
To use streamlink with the addon change the path in the configuration to the new streamlink executable and everything should work again.
Click on the button of the addon when on a twitch or hitbox stream (or youtube video) to launch livestreamer. This will open the stream in VLC (default, can be changed in the options).
Since version 2.0 any webservice supported by livestreamer can be handled with this addon. For the whole list of supported sites see:
If you need to supply any special parameters to livestreamer (retry rate, etc) you can do this aswell from the options.
Livestreamer needs to be installed
VLC icon by icons8