https://www.directory.trade-free.org/goods-services/vimix-gtk-theme/
Vimix-gtk-theme – Trade-Free Directory
Vimix is a flat Material Design theme for GTK 3, GTK 2 and Gnome-Shell which supports GTK 3 and GTK 2 based desktop environments like Gnome, Unity, Budgie,...
gtk themetradefreedirectory
https://www.omgubuntu.co.uk/2016/10/install-adapta-gtk-theme-on-ubuntu
How To Install the Adapta GTK Theme on Ubuntu - OMG! Ubuntu
gtk themeubuntu omginstall