% přesunout do ~/texexamples/packages
\documentclass[12pt]{article}
\usepackage{luatex85}
\usepackage[paperwidth=30em, paperheight=26em,margin=2em]{geometry}
\parindent=0pt
% \usepackage[***,postskip=1em,preskip=1em]{sectionbreak}
\usepackage[asterism]{sectionbreak}
\pagestyle{empty}

\begin{document}

Section separated by three exclamation marks.
\sectionbreak[!!!]

Section separated by asterism section mark requested in\\ \texttt{\textbackslash usepackage}.
\sectionbreak

Section separated by a rule.
\sectionbreakmark{\rule{10em}{3pt}}
\sectionbreak


\end{document}