Why is the uniq command not working properly?

Question

linux

There is a catalog. It contains other subdirectories, which in turn contains more subdirectories and files. I need to find duplicate names of files and directories in it. I tried the following command:
ls -1R /путь до основного каталога | uniq -D
No results.
Then I tried to do this:

ls -1R /путь до основного каталога > file
uniq -D file

Again there is no result, but it should be, because for the sake of experiment I copied one of the files to different subdirectories.
But if you create a file and add arbitrary text to it:

spoiler

Мой дядя самых честных правил
Когда не в шутку занемог
Когда не в шутку занемог
Он уважать себя заставил
И лучше выдумать не мог
И лучше выдумать не мог

Those expected result is.

Answer 1

Why is the uniq command not working properly?

Because it expects repeated lines to follow each other. You can insert sort before uniq into the pipeline to group the same lines.