Hyphenation doesn't work and lines overflow with French Babel (Lyx)

Question

I'm using texlive-babel-french (on Fedora) with Lyx, and text overflows instead of having clear cuts because of hyphenation. When I change language from French to English in Document > Preferences > Language, hyphenation works correctly, but LaTeX generated text (like Abstract) is not in French anymore, so I can't use the english package.

Edit: a sort of minimal example. I kept all Lyx code, because I don't know if it's of any use.

%% LyX 2.1.2 created this file.  For more info, see http://www.lyx.org/.
%% Do not edit unless you really know what you are doing.
\documentclass[12pt,a4paper,french]{article}
\usepackage[T1]{fontenc}
\usepackage[latin9]{inputenc}
\usepackage{babel}
\makeatletter
\addto\extrasfrench{%
   \providecommand{\og}{\leavevmode\flqq~}%
   \providecommand{\fg}{\ifdim\lastskip>\z@\unskip\fi~\frqq}%
}

\makeatother
\usepackage[unicode=true,pdfusetitle,
 bookmarks=true,bookmarksnumbered=false,bookmarksopen=false,
 breaklinks=false,pdfborder={0 0 0},backref=false,colorlinks=false]
 {hyperref}

\makeatletter

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% LyX specific LaTeX commands.
\pdfpageheight\paperheight
\pdfpagewidth\paperwidth


\makeatother

\begin{document}
Les \og visual guidelines \fg{} étaient complètes pour les usages
abordés, et la référence de l'API (qui explique chaque méthode) explicative
et claire. La documentation, quant à elle, laissait à désirer. Tout
comme d'autres documentations the rest is private information, sorry
:) but you can see how the text continues without any problem. But
I have long words like documentation documentation documentation documentation
documentationdocumentation documentation documentation documentation...
\end{document}

Answer 1

I had a similar hyphenation issue and fixed it by :

1. Turning the option Document / Settings / Language / Language package to None (to avoid the message "option clash for package babel").
2. Adding \usepackage[french]{babel} in Document / Settings / Latex preamble