As I have just replied to AdamHoles:
You can play DRM-defective DVDs on Trisquel. To do so, libdvdcss is required. It is free software, under the GNU GPL. https://code.videolan.org/videolan/libdvdcss hosts the code. However, Trisquel does not distribute the related libdvd-pkg package, probably because it is in Ubuntu's multiverse repository. You can download it from https://packages.ubuntu.com/xenial/all/libdvd-pkg/download and install it (by default, GDebi is installed and allows to simply double click on "libdvd-pkg_1.4.0-1-1_all.deb" in the file manager and then on a button to install).
