Search only by post_tags

search behaviour in wp to only search by post tags and not return results for titles or content if the tag is not found.

You can achieve this by customizing the search query using functions.php

function custom_search_filter($query) {
    // Check if it's the main query and it's a search query
    if ($query->is_main_query() && $query->is_search()) {
        // Get the search query
        $search_query = get_search_query();

        // Modify the query to only search for post tags
        $query->set('tag', $search_query);
    }
}
add_action('pre_get_posts', 'custom_search_filter');