I will go the opposite and say Debian. Mint had a major security breach a few months ago, to the point that someone edited their blog to give a download link to an image with a built-in backdoor (and edited the MD5 hash displayed on the site to match). Unsurprising since they used WordPress for their site, which is about as insecure a platform as you can get. Made me seriously question their proficiency. Debian is better-supported, with a much bigger userbase and longer history. It's free, and doesn't have any of the corporate entanglements you get with Ubuntu or Fedora. You can install whatever window manager you want (including MATE, which Mint uses by default) on Debian or any other distro. I personally used xfce on mine, since it's lighter than Gnome while still being quite user-friendly. Basically any WM is going to be pretty customizable. Here is my current UI.