Auto Disable Gutenberg
Auto Disable Gutenburg plugin will help you to disable new gutenburg block editor.You can disable Gutenberg completely. after active this plugin you can enable classic editor automaticly.
This section describes how to install the plugin and get it working.
Upload auto-disable-gutenburg folder to the
Activate the plugin through the ‘Plugins’ menu in WordPress
<?php do_action('auto_disable_gutenburg'); ?> in your templates
is this plugin will impact on my theme
No, this is a small size WordPress Plugin. it will assist to disable gutenburg plugin. no will have any harm or impact in your theme.