getEntityRecords/useEntityRecords: How to use CPT metadata?

Ok, I found the answer myself thanks to Can you filter posts by meta key with the getEntitityRecords selector?

Despite my first understanding the >>>query<<< parameters for list posts given in the Reference do >>>not<<< contain the meta.

I followed the article and created a query filter for the CPT, i.e.

    function mycustomposttype_meta_query_filter()
    {
      add_filter(
        'rest_mycustomposttype_query',
        function ($args, $request) {
          if ($meta_key = $request->get_param('metaKey')) {
            $args['meta_key'] = $meta_key;
            $args['meta_value'] = $request->get_param('metaValue');
          }
          return $args;
        },
        10,
        2
      );
    }

(NB the slug name ‘rest_mycustomposttype_query’ => you’ll need to adopt this to your custom post type) and added it in my CPT’s class constructor:

add_action('init', array($this, 'mycustomposttype_meta_query_filter'));

Now I can query as such

query.metaKey = 'customMetaKey';
query.metaValue = customMetaValue;

If anybody wants to contribute a more generic approach (multiple key/value meta query parameters) – welcome. This at least is sufficient to solve my current challenge.

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