This theme is not added to plugin index yet, so you need to install it manualy.
Simply clone this repo into your deploy/plugins directory.
$ cd LightTable/deploy/plugins
$ git clone https://github.com/vladimir-vg/ubuntu-lighttable-theme.git
When it's done you have to set it as a current theme in your user behaviors file.
Open Commands view, then Settings: User behaviors. Add behavior to editor object:
:editor [(:lt.objs.style/set-theme "ubuntu")]
You're done! Now you probably need to restart LT.
