selective-enable-blocks.php

<?php
function activate_gutenberg_for_post_type( $is_enabled, $post_type ) {
if ( 'post-type-name-here' == $post_type ) {
return true;
} elseif('page' == $post_type) {
  global $post;
  $pageTemplate = get_post_meta($post->ID, '_wp_page_template', true);
  if($pageTemplate == 'page-template-name-here.php') {
    return true;
  } else {
    return false;
  }
} else {
return false;
}
return $is_enabled;
}

add_filter( 'use_block_editor_for_post_type', 'activate_gutenberg_for_post_type', 10, 2 );
?>