/usr/share/myspell/dicts/fr_LU.dic is in hunspell-fr-classical 1:5.5-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/myspell/dicts/../../hunspell/fr.dic
/usr/share/myspell/dicts/../../hunspell/fr.dic