Pressbooks 5.9.0 has been released. Keyword: MathJax!
Upgrading requires a replacement for wp.com/latex.php which uses MathJax in place of WordPress’ LaTeX image rendering service. If you are unable or unwilling to install and host the pb-mathjax microservice, you may wish to install and network activate the WP QuickLaTeX plugin.
YAS Queen. -Carl Friedrich Gauss