After autoinstallation of Ispconfig 3.2.8 including all offered PHP versions, are there versions which I may deinstall manually later on without effecting the function of Ispconfig? Except 8.1?
You can uninstall any PHP version using apt (plus remove them in ISPConfig) as long as it's not the default PHP version of the OS. Plus, the PHP version must not be used by websites, of course.