Here is the new experimental version of MATE desktop environment for devuan beowulf, below the instructions to install it

Add the hezeh repo and install

Terminal

sudo echo "deb http://www.hezeh.org/packages beowulf main contrib non-free" >> /etc/apt/sources.list
sudo echo "deb-src http://www.hezeh.org/packages beowulf main contrib non-free" >> /etc/apt/sources.list
  

Terminal

sudo apt-get update; sudo apt-get install antofox-keyrings
  

Terminal

sudo apt-get install mate-desktop-environment
  

let me know if something is wrong