For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
Please see our announcement here.
{source}
<?php
$app = JFactory::getApplication();
$menuItem = $app->getMenu()->getActive();
$user = JFactory::getUser();
echo "Welcome " . $user->get('name') . " to " . $menuItem->title;
?>
{/source}