SearchWP has a related posts extension for generating a list of related posts based on their relevancy engine.
The metabox appears on all post types by default, and you can use the searchwp_related_excluded_post_types filter to exclude certain post types.
This often includes post types that have no need for related posts, like ACF field groups:
Rather than listing the excluded post types, I prefer specifying the few post types to include.
In the code below, I have an $allowed array listing the post types on which I’d like the metabox to appear. It then generate a list of all other post types and excludes SearchWP Related on those.
/**
* SearchWP Related on specific post types
* @link https://www.billerickson.net/searchwp-related-metabox-on-specific-post-types/
*/
function ea_searchwp_related_exclude( $exclude = array() ) {
$allowed = array( 'post', 'resource' );
$all = array_keys( get_post_types() );
return array_diff( $all, $allowed );
}
add_filter( 'searchwp_related_excluded_post_types', 'ea_searchwp_related_exclude' );