I have many duplicate photos in a folder. How can I sort the pictures in a folder by similarity? i.e., sorting not based on the file name or date, but based on similarity of image?
There is not a way to sort by picture similarity in most file browsers that I know of; and I have used many. It sounds like you need to look for a program that is designed to find duplicate pictures. There are many out there and what you use depends on your hardware/software setup. I have found that they are not 100% accurate so I usually use more than one program to find duplicates and then I still try and go through and see if I can find any. I use windows and have used auslogics duplicate file finder and anti-twin.
Images can be grouped by similarity but can't be sorted.
Some advanced programs allows you to specify a similarity degree, and another ones treat as duplicates only 100% identical photos.
Daminion allows you to find 100% similar images (as you requested) but file names and metadata part of your images can be different.
PS. I work at Daminion Software.