diff – How can I compare the source & destination paths with a different directory structure across different operating systems?

The source & destination paths have >100k different directories. I would like to compare the files between the source & destination without accounting for the differences between the directories.

Put another way, I want to match if the files in the source path are in the destination path. If there are differences, these would be outputted to a text file for example.

I need to be able to use a cross platform solution e.g. Windows & Linux.

How can I achieve this?