Disable WordPress Core, Plugins and Themes updates and Admin Notices

<?php
/*
Plugin Name:    Disable WP Updates
Plugin URI:     https://markokrstic.com
Description:    A simple plugin to disable WordPress updates.
Version:        1.2.0
Author:         Marko Krstic
Author URI:     https://markokrstic.com
License:        GPL2
Copyright:		© 2025, Marko Krstic
*/

function disable_wp_core_updates()
{
    // Disable core updates
    add_filter('pre_site_transient_update_core', '__return_null');
    // Disable plugin updates
    add_filter('pre_site_transient_update_plugins', '__return_null');
    // Disable theme updates
    add_filter('pre_site_transient_update_themes', '__return_null');
    // Disable update notifications
    remove_action('admin_notices', 'update_nag', 3);
}

add_action('init', 'disable_wp_core_updates');

// Disable automatic updates only
if (!defined('AUTOMATIC_UPDATER_DISABLED')) {
    define('AUTOMATIC_UPDATER_DISABLED', true);
}
if (!defined('WP_AUTO_UPDATE_CORE')) {
    define('WP_AUTO_UPDATE_CORE', false);
}

Scripts Organizer setup

If you are using Scripts Organizer you can set Location: Everywhere and Action plugins_loaded