Adding support for Post Tags to a CPT added by a plugin

You can use the register_taxonomy_for_object_type() function to associate the default post tags taxonomy with your custom post type.

Here’s an example code snippet that you can add to your Child Theme’s functions.php. Replace “your_custom_post_type” with the name of your custom post type.

function associate_tags_with_cpt() {
    register_taxonomy_for_object_type('post_tag', 'your_custom_post_type');
}
add_action('init', 'associate_tags_with_cpt');

https://developer.wordpress.org/reference/functions/register_taxonomy_for_object_type/