I'm having trouble getting the meta keys of custom categories. I tried dumping all the meta keys and values of a post by using get_post_meta() as such:
$myvals = get_post_meta($post->ID); var_dump($myvals);
However, the output doesn't include custom categories (not even the regular category). I made sure that my post does contain values in these categories so that they are not empty (in hopes that var_dump doesn't skip empty values). Some of the fields that are being printed are: custom fields keys, thumbnail key ("_thumbnail_id"), and some Yoast field keys that were included through a plugin.