Why doesn't ls -U list files in alphabetical order?
Solution 1:
As per man ls:
-U do not sort; list entries in directory order
Otherwise the default behavior is
Sort entries alphabetically if none of -cftu‐ vSUX nor --sort is specified
Directory order refers to the order in which the files are internally stored in the file system. Different FS:s use different criteria, so the order depends on the FS itself.