Filter to override the BP Attachments private directory

bp-custom.php

<?php
/**
 * BP Attachments overrides.
 */

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Changes the Private directory path in favor of:
 * `/wp-content/uploads/buddypress/private`.
 * 
 * NB: you need to take care of privacy by yourself in this case.
 * 
 * @return string Path to the private directory.
 */
function return_bp_attachments_private_dir_override() {
    return trailingslashit( bp_attachments_uploads_dir_get( 'basedir' ) ) . 'private';
}
add_filter( 'bp_attachments_pre_get_private_root_dir', 'return_bp_attachments_private_dir_override' );