I'm bit unsure of your motivations, intent. terminology and so forth -
A. Everything XAMPP needs and wants (other than a running Linux OS) is in the /opt/lampp folder. There are generally no other dependencies other than ia32 Libraries for 64 bit distros,
B. The owner of /opt/lampp should be nobody:root (owner:group). Try changing it to that and see if it works.
C. Just be aware XAMPP/lampp is not a LAMP stack - its a bash script that runs everything via CLI calls. its worth opening lampp and seeing what it is doing.
I can clarify what your original error 'means' at a fundamental level: PHP is not running, probably due to some error. That's why it wants you to DL the page (it can't be parsed) I'd make that change (above) and if that does not resolve your issue, look in /opt/lamp/log/error_log (Apache) and /opt/lamp/log/php_error_log