I believe Ubuntu also ships a tool for changing the theme in the default install. However the upstream (Gnome) is adversarial to this (https://news.ycombinator.

I believe Ubuntu also ships a tool for changing the theme in the default install. However the upstream (Gnome) is adversarial to this (https://news.ycombinator.com/item?id=20376442 https://news.ycombinator.com/item?id=20376442).