There is a new theme set available on Gnome Look. This makes Linux look just like Macintosh OSX High Sierra. It is very high quality and well worth installing.
The GTK3 theme: https://dl.opendesktop.org/api/files/download/id/1537895905/s/a13d96c5494b48d7c715859105db2c5d/t/1537916795/u//Sierra-light.tar.xz.
Cursor theme: https://dl.opendesktop.org/api/files/download/id/1517130771/s/a13d96c5494b48d7c715859105db2c5d/t/1537916795/u//MacOSX-cursors.tar.xz.
A couple of Mac OSX wallpapers: https://dl.opendesktop.org/api/files/download/id/1517131134/s/a13d96c5494b48d7c715859105db2c5d/t/1537916795/u//HighSierra-wallpapers.tar.xz.
Unpack the GTK theme under the ~/.themes folder. And the icon theme under the ~/.icons folder. Then go to System->Preferences->Look and Feel->Appearance and select the themes with the Customize option. Then the MATE desktop will look like this. It really is very attractive and clean for a desktop theme.
![Mac OSX styled MATE desktop on Linux.](https://www.securitronlinux.com/wp-content/uploads/2018/09/macosx-960x540.png)
It is one of the best looking themes for Linux. I highly recommend installing it and themeing your MATE desktop to look just like a modern MacOS 10.12.6 machine, and that is pretty cool indeed.
![Mac OSX theme on MATE with window buttons on left.](https://www.securitronlinux.com/wp-content/uploads/2018/09/macosx2-960x540.png)
Compare it to the real thing. And notice it just exactly the same. That is how well the theme was made.
![Mac OS Sierra desktop.](https://www.securitronlinux.com/wp-content/uploads/2018/09/desktop-960x600.png)
Use the MATE Tweak tool to set the window buttons to the left. This completes the look.