<?php

//Disable Gutenberg for all but keep Enabled for Blog Posts only
function wm_gutenberg_disable_cpt($can_edit, $post_type){
  if($post_type != 'post'){
    $can_edit = false;
  }
  return $can_edit;
}
add_filter('gutenberg_can_edit_post_type', 'wm_gutenberg_disable_cpt', 10, 2);