marklar said almost 3 years ago on Fixing Assets in CSS Bundling for Rails :
  Stephane PAQUET have you been able to get fontawesome working in production with this approach? 

@import '@fortawesome/fontawesome-pro/css/all';
@tailwind base;
@tailwind components;
@tailwind utilities;

For me, this works in development, however, the fonts aren't displayed correctly when deployed to Heroku.

Do you know the correct path to use in manifest.js when importing fontawesome into application.tailwind.css?