Populate ACF Select Field with WooCommerce Attributes.

acf-select-wc-attributes.php

<?php
/**
 * Populate ACF Select Field with WooCommerce Attributes.
 */
add_filter('acf/load_field/name=featured_attributes', function($field) {
    $taxonomies = get_taxonomies([
        'public' => false,
        '_builtin' => false
    ], 'objects');

    $field['choices'] = [];

    /** @var \WP_Taxonomy $taxonomy */
    foreach($taxonomies as $taxonomy) {
        // Exclude non-woocommerce choices:
        if(strncmp('pa_', $taxonomy->name, 3) !== 0) {
            continue;
        }

        $field['choices'][$taxonomy->name] = $taxonomy->label;
    }

    return $field;
});