WordPress - Verifying nonce with navigator.sendBeacon - wordpress

Question

I am working on a very simple tracking plugin. I am using the visibilitychange event to send tracking data to a PHP script included in the plugin using navigator.sendBeacon.
However, unlike a simple WordPress AJAX request, the PHP file doesn't have access to any of the WordPress core files. Therefore the check_ajax_referer function throws an error.
I can't figure out a way of ensuring the PHP file has access to the WordPress core files, or even any of the files I have included in the plugin.
Is it possible to set this up like is normally done with WP and AJAX, or do I need to include all of the WP core files in the PHP script? And, if the second option is the only option, which files do I need to include?
Example code:
Enqueuing the JS script and localizing the PHP script path and nonce:
wp_enqueue_script( $this->plugin_name, plugin_dir_url( __FILE__ ) . 'dist/scripts/main.js', array( 'jquery' ), $this->version, true );
wp_localize_script( $this->plugin_name, 'OBJECT_NAME', array('PHP_SCRIPT_PATH' => PATH, 'ajax_nonce' => wp_create_nonce('TRACKING_NONCE')));
Send the data
document.addEventListener("visibilitychange", function () {
if (document.visibilityState === 'hidden') {
var data = new FormData();
data.append('tracking_data', JSON.stringify(form_data));
navigator.sendBeacon(OBJECT_NAME.PHP_SCRIPT_PATH, data);
}
});
Receive and process the data:
if (!empty($_POST)) {
$security_check = check_ajax_referer( 'TRACKING_NONCE', 'security' ); //Error thrown: Uncaught Error: Call to undefined function check_ajax_referer()
//Process data....
}