\documentclass{article}
\renewcommand{\cuttingunit}{section}
\flushdef{part}
\setcounter{cuttingdepth}{2}.
\begin{document}
\title{Coucou\footnote{Coucou} --- Toi\footnote{Toi}}
\author{Moi\thanks{Moi}}
\date{Aujourd'hui}
\maketitle
\begin{quote}
Non-default \hacha{} behavior for \texttt{article}:
cut at sections, flush footnotes at parts.
\end{quote}
\part{Grand un}
\section{Un}
Un\footnote{un}.
\subsection{Un-Un}
Un-Un~\footnote{un-un}.
\subsection{Un-Deux}
Un-Deux~\footnote{un-deux}.


\subsection{Un-Trois}
Un-Trois~\footnote{un-trois}.
\subsubsection{Un-Trois-Un}
Un-Trois-Un~\footnote{un-trois-un}.
\subsubsection{Un-Trois-Deux}
Un-Trois-Deux~\footnote{un-trois-deux}.



\subsection{Un-Quatre}
Un-Quatre~\footnote{un-quatre}.
\section{Deux}
Deux\footnote{deux}.
\section{Trois}
Trois\footnote{trois}.
\part{Grand deux}
\section{Quatre}
Quatre\footnote{quatre}.
\end{document}
