No, it doesn't help, because my post is referring specifically to Font Awesome 5 (your example is fa = Font Awesome 4). I'm referring to using Font Awesome 5, as with the code below "fab".
Using FA5 is working OK in the browser:
However, in the Moodle App the images are missing:
What I'm trying to understand is whether the Moodle App "CAN" support Font Awesome 5 ?
Can it support the stacking function ?
If it can, how would that be enabled ?
Currently I've used the following code, which works great in browsers, but not the Moodle App:
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.0.13/css/all.css" integrity="sha384-DNOHZ68U8hZfKXOrtjWvjxusGo9WQnrNx2sqG0tfsghAvtVlRW3tvkXWZh58N9jp" crossorigin="anonymous"></script>
Moodle web and Moodle apps currently support FontAwesome 4.7.0. However you can add code to support FA > 5.
I think your problem is that you didn't add brands css. If you check this site, you'll see brands are in a separate css file:
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.2.0/css/brands.css" integrity="sha384-nT8r1Kzllf71iZl81CdFzObMsaLOhqBU1JD2+XoAALbdtWaXDOlWOZTR4v1ktjPE" crossorigin="anonymous">
You can try that to add support, however I'm not sure why is working on your website (problably 4.7 has any compatibility). Please check it again and check the fontawesome documentation for further help.