How to overwrite registered taxonomy url from vendor plugin in child theme

by

You don’t need those custom rewrites and term permalink tweaks, so just remove these and the relevant callbacks:

add_action('init','theme_child_custom_rewrite', 1000);
add_filter( 'term_link', 'listing_region_term_link', 1, 3 );

And just use the register_taxonomy_args hook to override the taxonomy’s parameters:

function override_listing_region_taxonomy_args( $args, $taxonomy ) {
    if ( 'listing-region' === $taxonomy ) {
        $args['rewrite'] = array(
            'slug' => 'region',
        );
    }
    return $args;
}
add_filter( 'register_taxonomy_args', 'override_listing_region_taxonomy_args', 11, 2 );

Things to note:

  1. Make sure you flush the permalinks after applying the above code/changes — just visit the permalink settings page (without making any changes or clicking the submit button).

  2. You may need to use a greater priority value; e.g. 20:

    add_filter( 'register_taxonomy_args', 'override_listing_region_taxonomy_args', 20, 2 );