This is problem specific to tex4ht only.
When compiling this MWE
\documentclass[11pt]{article}
\usepackage{amsmath}
\begin{document}
\[%
\begin{array}
[c]{c}%
\text{{\small bottom edge}}\\
\text{{\small bottom edge}}\\
\end{array}%
\begin{bmatrix}
\alpha & 2\\
1 & \alpha \\
\end{bmatrix}%
\]
\end{document}
Using the command
make4ht -ulm default foo.tex "htm,mathjax"
The HTML output looks like this
When compiling the same file using lualatex foo.tex the output in pdf looks like
How to make tex4ht output the same as in the pdf?
The raw HTML generated by tex4ht is
<!DOCTYPE html>
<html lang="en-US" xml:lang="en-US" >
<head><title></title>
<meta charset="utf-8" />
<meta name="generator" content="TeX4ht (https://tug.org/tex4ht/)" />
<meta name="viewport" content="width=device-width,initial-scale=1" />
<link rel="stylesheet" type="text/css" href="foo.css" />
<meta name="src" content="foo.tex" />
<script> window.MathJax = { tex: { tags: "ams", inlineMath: [ ["\\\(","\\\)"] ], displayMath: [ ['$$','$$'], ["\\[","\\]"] ], processEscapes: true, processEnvironments: true, packages: ['base', 'color', 'ams'] }, loader: { load: ['[tex]/color', '[tex]/ams'] } }; </script>
<script type="text/javascript" async="async" id="MathJax-script" src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-chtml-full.js"></script>
</head><body
>
<!--l. 18--><p class="noindent" >\[\begin{array} [c]{c}\text{{\small bottom edge}}\\ \text{{\small bottom edge}}\\ \end{array}\begin{bmatrix} \alpha & 2\\ 1 & \alpha \\ \end{bmatrix}\] </p>
</body>
</html>
Using TL 2020 on Linux
