Luxembourgish language files
If you wish to (and you should) upgrade to LibreOffice as your preferred Office Suite and you write documents in Luxembourgish then you may need the language files as they are not included yet in the standard distribution.
Installation on Debian/Ubuntu
Copy the dictionary files you downloaded in the right directory:
sudo cp lb_LU.aff lb_LU.dic /usr/share/hunspell/ sudo chown root:root /usr/share/hunspell/lb_LU.*
Copy the thesaurus files you downloaded in the right directory:
sudo cp th_lb_LU_v2.dat th_lb_LU_v2.idx /usr/share/mythes/ sudo chown root:root /usr/share/mythes/lb_LU.*