What command will show the presence of files in large and small register in the same directory at the same time?

Question

linux

It is necessary to understand whether there are files in a given directory (including nested directories) that occur simultaneously in large and small register in the same folder.
It is desirable that this list be output to a file.
Example:

/data/folder1/file.txt
/data/folder1/File.txt
/data/folder2/image.img
/data/folder2/IMAGE.img

Answer 1

more or less like this:
find -type f | sort --ignore-case | uniq -D -i

Answer 2

There are many options. You can, for example, display a list of files, convert it to lowercase and look for duplicates.