For people following this guide if you get errors with AlpineJS you need to change the target from es2016 to a minimum of es2017.

# Configure esbuild (the version is required)
config :esbuild,
  version: "0.13.10",
  default: [
    args:
      ~w(js/app.js --bundle --target=es2017 --outdir=../priv/static/assets --external:/fonts/* --external:/images/*),
    cd: Path.expand("../assets", __DIR__),
    env: %{"NODE_PATH" => Path.expand("../deps", __DIR__)}
  ]

For google the errors you’ll see are:

module.esm.js:1635 Alpine Expression Error: func(...).catch is not a function

module.esm.js:1701 Uncaught TypeError: func(...).catch is not a function
    at module.esm.js:1701
    at tryCatch (module.esm.js:1628)
    at evaluate (module.esm.js:1646)
    at module.esm.js:2998
    at Function.<anonymous> (module.esm.js:2390)
    at flushHandlers (module.esm.js:1757)
    at stopDeferring (module.esm.js:1762)
    at deferHandlingDirectives (module.esm.js:1765)
    at initTree (module.esm.js:1953)
    at module.esm.js:1921

Just to offer an alternative solution how to add a font file, you can also include the font using the postcss-url plugin as follows. (cc @cvkmohan )

1. Place the font in assets/fonts

I only need the one variable font file in WOFF2 format so for me it’s at assets/fonts/Inter.var.woff2.

2. Add postcss-url dependency

npm install postcss-url --save-dev

3. Add the plugin to assets/postcss.config.js

Mine looks like this after adding it:

module.exports = {
  plugins: {
    'postcss-import': {},
    'postcss-url': { url: 'inline' },
    tailwindcss: {},
    autoprefixer: {},
  }
}

4. Add the @font-face definition to your app.css

@font-face {
  font-family: 'Inter';
  font-weight: 1 999;
  src:
    url('../fonts/Inter.var.woff2') format('woff2-variations');
}

–

The above configuration will inline the font into your CSS like this:

@font-face { font-family: "Inter"; src: url("data:font/woff2;base64,d09G[...]d6eMC") format("woff2-variations"); font-weight: 1 999; }

If you prefer to keep the font(s) in separate files, use copy instead of inline.

not quite as easy as @thomas.fortes suggests..

but close if you are OK with a seperate css file for the font (face) and thus using esbuild for it..

• download the font Inter font family
• copy the Inter Web folder into say /assets/vendor/fonts and rename the folder to InterWeb (need to avoid spaces!)
• change the esbuild args in config.exs to:
  ~w(js/app.js vendor/fonts/InterWeb/inter.css --bundle --loader:.woff2=file --loader:.woff=file --target=es2016 --outdir=../priv/static/assets),
• notice that the app.js is now outputted inside a js folder
  go to your layout and change the js script src to Routes.static_path(@conn, "/assets/js/app.js")
• above your app.css stylesheet do a:
  <link phx-track-static rel="stylesheet" href="<%= Routes.static_path(@conn, "/assets/vendor/fonts/InterWeb/inter.css") %>"/>

for bonus points:
add GitHub - semencov/tailwindcss-font-inter: TailwindCSS Plugin to integrate with Inter Typeface · GitHub by doing:
npm install --save-dev tailwindcss-font-inter (in the assets folder)
and then add the plugin in the tailwind config:

  plugins: [require('tailwindcss-font-inter')({ 
    importFontFace: false,
  })]

now you can use the css class font-inter wherever you want..