To disable updates for a WordPress plugin, add this code to functions.php

function AS_disable_plugin_updates( $value ) {
  //create an array of plugins you want to exclude from updates ( string composed by folder/main_file.php)
   $pluginsNotUpdatable = [
    'plugin1/plugin.php',
    'plugin2/plugin2.php'
  ];

  if ( isset($value) && is_object($value) ) {
    foreach ($pluginsNotUpdatable as $plugin) {
        if ( isset( $value->response[$plugin] ) ) {
            unset( $value->response[$plugin] );
        }
      }
  }
  return $value;
}
add_filter( 'site_transient_update_plugins', 'AS_disable_plugin_updates' );