It is possible to use Offline MathJax in playcanvas.
You can use it with HTML elements that are on top of the PlayCanvas view but not really as part of the native UI elements system or in the WebGL context.
As one of it’s outputs is SVG, you could render that in the WebGL context by rendering into the data and generating a mesh.
Not sure what you mean by ‘offline MathJax’ as it’s a rendering library from what I can see.
Present i’m working on lab simulations. Which are used in tabs. In that we use WEB GL formats not as a PlayCanvas links.
CDN link of MATHJAX works on online only. Here we are using in offline. For this we can use MathJax offline folder. I don’t know it support are not.
As far as I can tell, there is no requirement for MATHJAX to be ‘online’. It’s just a JS library file that you can host yourself or copy into PlayCanvas.