How to add add blank non-editable wp page like default blog for use with plugin

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You can do it by hooking admin_init action:

  1. First, you can create a option to select the page you create for your plugin. I suppose that the option will be save in wp_options table with name your_plugin_special_page.

  2. Remove editor support on that page with this action.

    add_action( 'admin_init', 'your_plugin_hide_editor' );
function your_plugin_hide_editor() {

    // Get the Post ID
    if ( isset( $_GET[ 'post' ] ) ) {
        $post_id = $_GET[ 'post' ];
    } elseif ( isset( $_POST[ 'post_ID' ] ) ) {
        $post_id = $_POST[ 'post_ID' ];
    }
    if ( !isset( $post_id ) ) {
        return;
    }

    // Remove editor support
    if ( get_option('your_plugin_speical_page') == $page_id ) {
        remove_post_type_support( 'page', 'editor' );
    }
}

  3. Then you can use admin notices to display your message to user (https://codex.wordpress.org/Plugin_API/Action_Reference/admin_notices)

Hope this help!