Linking external JSON-LD schema (from Schema.org)

This may, or may not help, but take a look at how Trevor Fox did it:

<script>

$.getJSON( "/your-schema-file.jsonld", function( data ) {
$( "<script/>", {
"type": "application/ld+json",
"html": JSON.stringify(data)
}).appendTo( "head" );
});

</script>

This may be your best option. He used jQuery version 3.1.1 for this solution.

According to the documentation:

[…] Also, Google can read JSON-LD data when it is dynamically injected into the page's contents, such as by JavaScript code or embedded widgets in your content management system.

Which suggests that, while yo cannot link external json-ld data, you can still load it dynamically and inject it to the DOM. This might be good enough for your use case, as you can load static JavaScript on your page that will then inject the JSON-LD into the DOM.

unor’s answer sums it up, but I also want to add:

From the spec:

Setting the [type] attribute to any other value [other than a JavaScript MIME type] means that the script is a data block, which is not processed. None of the <script> attributes (except type itself) have any effect on data blocks. Authors must use a valid MIME type that is not a JavaScript MIME type to denote data blocks.

So, in other words, if you have a <script> with a type attribute set to anything other than text/javascript (or an equivalent JavaScript MIME type), then all attributes, including src, will have no effect.

The script element can be used for two things:

• dynamic/classic scripts
• data

And for data, the spec defines:

When used to include data blocks, the data must be embedded inline […]

So you may use the src attribute only for scripts, not for data.

→ As JSON-LD is data, you have to inline it.

While linking a JSON-LD file is possible with the link element, the Schema.org sponsoring search engines don’t seem to support it.