Admin Notice is a very simple plugin that allows you to display custom notices in the WordPress admin that is visible to all users.
Control over the notice text and styling is available from the plugin’s settings page.
Developers can use the admin_notice_enable hook to control the notice’s visibility on a more granular level. The following example demonstrates how to show the notice only in the “Posts” area of the admin.
add_filter('admin_notice_enable', function($enabled) {
$screen = get_current_screen();
if (isset($screen->post_type) && $screen->post_type !== 'post') {
$enabled = false;
}
return $enabled;
}, 10, 1);
This plugin is available for download for your site.