/usr/share/myspell/dicts/fr_LU.dic is in hunspell-fr-comprehensive 1:6.2-1.
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