Hi, sorry I missed this - I seemed to misunderstand the question. There's a simple fix that I guess I might now make an extension either today or tomorrow depending when I have free time.

Here's how you could do it on your own, this is for the google cloud docs reference https://cloud.google.com/compute/docs/apis.

Note you have to allow pages to set their own fonts in firefox if you use this option

0. Open up your console in dev-tools (F12).

1. Load Jquery (Give it a second, let the script load)

  var jq = document.createElement('script');
  jq.src = "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js";
  document.getElementsByTagName('head')[0].appendChild(jq);

2. See all the font-families the page is using

  fontSets = new Set();
  $('*').each( function() {
    fontSets.add( $(this).css("font-family"))
  });
  console.log(fontSets)

for google cloud docs this reveals:

  Set(7) [ 
    "Roboto, Noto Sans, Noto Sans JP, Noto Sans KR, Noto Naskh Arabic, Noto Sans Thai, Noto Sans Hebrew, Noto Sans Bengali, sans-serif", 
    "\"Material Icons\"", 
    "Google Sans, Noto Sans, Noto Sans JP, Noto Sans KR, Noto Naskh Arabic, Noto Sans Thai, Noto Sans Hebrew, Noto Sans Bengali, sans-serif", 
    "Roboto, RobotoDraft, Arial, sans-serif", 
    "Roboto, RobotoDraft, Helvetica, Arial, sans-serif", 
    "Google Sans, Roboto, RobotoDraft, Helvetica, Arial, sans-serif", 
    "Material Icons"]

3. Make an educated guess, I guess its probably Material Icons that OpenDyslexic is messing up, so lets update all the font-families that don't contain Material Icons

  $('*').each( function() {
    if ( $(this).css("font-family").indexOf("Material Icons") === -1)
      $(this).css("font-family",`OpenDyslexic, ${$(this).css("font-family")}`);
  });