Disable notices in WordPress dashboard

functions.php

<?php

/**
 * Disable admin notices for all.
 */

function _action_disable_admin_notices() {
  
  global $wp_filter;

  if ( is_user_admin() ) {
    if ( isset( $wp_filter['user_admin_notices'] ) ) {
      unset( $wp_filter['user_admin_notices'] );
    }
  } elseif ( isset( $wp_filter['admin_notices'] ) ) {
    unset( $wp_filter['admin_notices'] );
  } // end if is_user_admin()

  if ( isset( $wp_filter['all_admin_notices'] ) ) {
    unset( $wp_filter['all_admin_notices'] );
  }

}
add_action( 'admin_print_scripts', '_action_disable_admin_notices' );

/**
 * Disable update notices for all users with exceptions.
 */

function _action_disable_update_notices() {
  
  $current_user       = wp_get_current_user();
  $current_user_login = $current_user->user_login;

  if ( $current_user_login != 'adminusername' ) {
    remove_action( 'load-update-core.php', 'wp_update_plugins' );
    add_filter( 'pre_site_transient_update_plugins', '__return_null' );
  }
  
}
add_action( 'admin_head', '_action_disable_update_notices' );

/**
 * Disable update notices for all.
 */
remove_action( 'load-update-core.php', 'wp_update_plugins' );
add_filter( 'pre_site_transient_update_plugins', '__return_null' );