Installing XAMPP on Linux:

Change the permissions to the installer

chmod 755 xampp-linux-*

Run the installer

sudo ./xampp-linux-*

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Stop Xampp, if running.
Rename the /opt/lampp folder to /opt/lampp-old (or whatever), then install a new lampp.
Finally copy the whole /opt/lampp-old/htdocs folder to the new release (/opt/lampp/htdocs, previously rename the newly installed htdocs folder to htdocs-original or so) and same for the mysql data, copy the whole /opt/lampp-old/var/mysql to /opt/lampp/var/mysql (and also rename mysql folder from newly installed Xampp before). Be sure to keep the same file permissions and users of the copied folders.