Inserted wide figure in two-column document going to the next page when there is enough height and width

Question

Here's my document:

\documentclass[twocolumn]{article}
\usepackage[utf8]{inputenc}
\usepackage{geometry}
\usepackage{ctex}
\usepackage{enumitem}
\usepackage{mathtools}
\usepackage{flushend}
\usepackage{graphicx}
\usepackage{caption}
\usepackage{longtable}
\usepackage[normalem]{ulem}
\usepackage{amssymb}
\usepackage{multicol}
\usepackage{framed}
\usepackage{changepage}
\usepackage{lettrine}
\usepackage{tikz}
\usepackage{lipsum}
\usepackage{wrapfig}
\usepackage{xcolor}
\usepackage{sidecap}
\usepackage{lilyglyphs}
\usepackage{balance}

\setlength{\columnsep}{0.75cm}

\geometry{paperheight=24cm,paperwidth=24cm,left=1.5cm,right=1.5cm,top=1.5cm,bottom=2.5cm}

\title{test}
\author{}
\date{\today}

\begin{document}

\balance

\large \lipsum[1]

\begin{figure*}[hbt!]
    \centering
    \includegraphics[width=10cm]{8_group.png}
    \caption*{Caption 1}
    \caption*{Caption 2}
\end{figure*}

\end{document}

and here is the output:

There's clearly enough space underneath the text for the image. How do I make the image directly below the text?

I'm using LuaLaTeX (TeX Live 2021) (Overleaf).

Answer 1

If you use the twocolumn class option, multicolumn floats can only be placed at the top of the next page (or on float pages).

If you want to have your figure somewhere else, you can use the multicolumn package instead (which you already load)

\documentclass[
%twocolumn
]{article}
\usepackage[utf8]{inputenc}
\usepackage{geometry}
%\usepackage{ctex}
\usepackage{enumitem}
\usepackage{mathtools}
\usepackage{flushend}
\usepackage{graphicx}
\usepackage{caption}
\usepackage{longtable}
\usepackage[normalem]{ulem}
\usepackage{amssymb}
\usepackage{multicol}
\usepackage{framed}
\usepackage{changepage}
\usepackage{lettrine}
\usepackage{tikz}
\usepackage{lipsum}
\usepackage{wrapfig}
\usepackage{xcolor}
\usepackage{sidecap}
\usepackage{lilyglyphs}
\usepackage{balance}

\setlength{\columnsep}{0.75cm}

\geometry{paperheight=24cm,paperwidth=24cm,left=1.5cm,right=1.5cm,top=1.5cm,bottom=2.5cm}

\title{test}
\author{}
\date{\today}

\begin{document}

\begin{multicols}{2}
\large \lipsum[1]
\end{multicols}
\begin{figure*}[hbt!]
    \centering
    \includegraphics[width=10cm]{example-image-duck}
    \caption*{Caption 1}
    \caption*{Caption 2}
\end{figure*}
\begin{multicols}{2}
\large \lipsum[1]
\end{multicols}

\end{document}