Lorenzo-
 This issue is specific to some versions of Linux. For Windows users, the software ships with Python 3. For MacOS users, the software works nicely with the version of Python 2.7 that ships with MacOS (e.g. 2.7.16). However, the version of Python 2.7 that comes with some versions of Linux (e.g. 2.7.15+) does not have modern unicode support. If you run Surfice from the command line you will see the following error when you run Surfice:
  Error: could not find symbol "PyUnicode_FromWideChar"

I think there are two options:
 1. Upgrade to a modern version of Python 2.7
 2. Leave Python 2.7 unchanged, but install Python 3. I think this would be either "sudo apt-get install python3.6" or "sudo apt-get install python3".

Once you have installed a modern version of Python on your computer, it is probably worth starting Surfice from the command line with the -R option "surface -R" which will reset defaults and should cause it to auto-detect the more modern version of Python (I think you can also launch the graphical version with the Control key down).