there is probably a better way - say a plugin that checks if the scrip it vbadcanced and send directly to the forums home...
Easier - You could edit the adv_portal template and replace with something like this:
Code:
$stylevar[htmldoctype]
<html>
<head>
$headinclude
<meta http-equiv="Refresh" content="2; URL=forum.php" />
</head>
<body>
$header
$navbar
<div align="center"><a href="forum.php">Portal Disabled in Mobile View - Click here if your browser does not automatically redirect you.</a></div>
$footer
</body>
</html>