Para os próximos 14 meses, eu recomendo criar o schroot com o Ubuntu 16.04 LTS dentro dele e instalar o FreeFileSync nele:
sudo apt-get install schroot debootstrap -y
cat <<EOF | sudo tee /etc/schroot/chroot.d/xenial.conf
[xenial]
description=Ubuntu 16.04 Xenial
directory=/srv/chroot/xenial
root-users=$USER
type=directory
users=$USER
EOF
sudo mkdir -p /srv/chroot/xenial
sudo debootstrap xenial /srv/chroot/xenial
cat <<EOF | sudo tee /srv/chroot/xenial/etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu xenial main universe multiverse
deb http://security.ubuntu.com/ubuntu xenial-security main restricted universe multiverse
EOF
schroot -c xenial -u root apt-get update
schroot -c xenial -u root apt-get install software-properties-common sudo
schroot -c xenial -u root apt-get install libgtk2.0-0 libsm6 # for FreeFileSync
Então você pode baixar o FreeFileSync como de costume
cd ~/Downloads
wget http://download936.mediafire.com/qayx2xg6bkyg/rhia0pqcfqjmu2w/FreeFileSync_9.7_Ubuntu_16.04_64-bit.tar.gz
# if wget does not work download it manually to ~/Downloads
tar -xvzf FreeFileSync_9.7_Ubuntu_16.04_64-bit.tar.gz
Em seguida, tente iniciá-lo no terminal
schroot -c xenial env DISPLAY=:0.0 ~/Downloads/FreeFileSync/FreeFileSync
Se funcionar, você pode criar um atalho na área de trabalho da seguinte maneira:
cat <<EOF > ~/Desktop/FreeFileSync.desktop
[Desktop Entry]
Name=FreeFileSync
Comment=Keep files and folders synchronized
Exec=schroot -c xenial env LC_ALL=en_US.UTF-8 DISPLAY=:0.0 /home/$USER/Downloads/FreeFileSync/FreeFileSync
Terminal=false
Type=Application
Icon=freefilesync
MimeType=application/x-freefilesync-ffs;application/x-freefilesync-batch
Categories=Utility;FileTools;GTK;
StartupWMClass=FreeFileSync
StartupNotify=true
EOF
chmod +x ~/Desktop/FreeFileSync.desktop