Ubuntu Linux 20.04 comes with PHP 7.4. Some web site code written in the PHP 5 (or earlier) era is not compatible with that version of the hypertext preprocessor and will break under a new OS build with all up-to-date binaries.
If your business’ digital infrastructure is run by “a guy you know,” you might be in trouble. Even if that guy is your best friend from kindergarten, a genius in his own right, and doesn’t even wear a fedora or ride a skateboard to the office.
“Statistics allow you to do exactly the wrong thing, but with 99 percent confidence.” Not sure if that’s how the saying goes, but perhaps it should.