Unicode is the international standard for encoding the text of all the world's languages. Sally uses Unicode throughout, so file and directory names in any language, and paths longer than the classic limit of 260 characters, work the same way as plain English names.
Sally displays and works with names in any script: Greek, Cyrillic, Chinese, Japanese, Korean, Arabic, Hebrew, accented Latin, symbols, and so on. They work in the panels and with copy, move, delete, rename, quick rename, change attributes, create directory, drag & drop, the clipboard, directory history, hot paths, Find and its results, viewing, editing, and the command line. Paths can be up to 32,767 characters long, including network (UNC) paths.
Your Windows language settings do not matter for this: Sally does not depend on the "Language for non-Unicode programs" setting.
The internal viewer opens text files with a UTF-8 or UTF-16 byte-order mark decoded, and Hex mode always shows the raw bytes. Use the Convert command to convert text files between encodings and line endings, and the File Comparator plugin to compare files saved in different encodings.
Some data still travels in older, non-Unicode formats. Sally converts names once, at that boundary, and refuses an operation rather than act on a different file when a name cannot be represented: