Thank you for your extensive answer/tutorial but I would have liked a simple freeware.Regarding File Explorer being cumbersome - likely so.
Consider using Powershell: may seem cumbersome or complicated at first but may be very straightforward and simple once you get a sense of it all.
FYI:
https://collectingwisdom.com/powershell-compare-two-folders/
https://stackoverflow.com/questions...ell-script-to-compare-two-folders-recursively
You can easily find similar "how-to's" and tutorials. Simple to complex.
Google "Powershell how to compare folders" to start and then revise the search criteria as you read and learn.
Powershell is built into Windows and it is very easy to copy cmdlets and scripts to test.
Just be sure that all testing is done using copies of the target folders and well away from any possible connection path to the real data. Which should be backed up somewhere else for added protection.
You are a moderator on a distinguished computer forum thus what you consider simple is probably complicated for me.
Thanks anyways.....