I've used a Free program on and off now for awhile. It's called SimilarImages. It's available from https://tn123.org/simimages/
It's pretty simple to use. I don't think I've ever changed the settings here. Just open the program and click on the plus sign icon to add folder(s). High lite and use the minus sign to remove items from the list. The trash can one clears the list. And click on the magnifying glass icon to start the scan.
I copied a few of my pictures to a folder called temp and duplicated one on purpose. I clicked on the plus sign icon to add the temp folder to the list. Then I click on the magnifying icon to scan. I only had 19 pictures in all with only one duplicate. It found it and using one of the red x's I can chose to delete one copy or the other. That's all is to it.
