TL;DR

Set processEscapes to False or remove it from tax dictionary

<script>
MathJax = {
  tex: {
    inlineMath: [['$', '$'], ['\\(', '\\)']],
  },
  svg: {
    fontCache: 'global'
  }
};
</script>
<script type="text/javascript" id="MathJax-script" async
  src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-svg.js">
</script>

What was not working

I’ve tried to write blog posts using Obsidian for my Jekyll website. The issue was the Mathjax version I was using didn’t recognize single dollar sign for inline equations.

I was using this Mathjax setup taken from the documentation:

<script>
MathJax = {
  tex: {
    inlineMath: [['$', '$'], ['\\(', '\\)']],
    processEscapes: true
  },
  svg: {
    fontCache: 'global'
  }
};
</script>
<script type="text/javascript" id="MathJax-script" async
  src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-svg.js">
</script>

But the \$ signs in my markdown was displaying as \$ in the rendered HTML. Some of the related answers mentioned the issue of markdown + Mathjax processing order.

I’ve tried different inlineMath options, but at the end downgrading to 2.x version solved the problem.

 <script type="text/javascript" async src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.6/MathJax.js?config=TeX-MML-AM_CHTML">
 </script>
 <script type="text/x-mathjax-config">
    MathJax.Hub.Config({
      extensions: ["tex2jax.js"],
      jax: ["input/TeX", "output/HTML-CSS"],
      tex2jax: {
        inlineMath: [ ['$','$'], ["\\(","\\)"] ],
        displayMath: [ ['$$','$$'], ["\\[","\\]"] ],
      },
      "HTML-CSS": { availableFonts: ["TeX"] }
    });
 </script>

However after trying with options later, turns out just removing processEscapes seem to solve the problem.