for those who want to list notebooks in their Workspace directory, try:

dbutils.fs.ls("file:/Workspace/Users/<your_email>")

This will list the files in your user's personal workspace in databricks. Note: file: at the beginning of the path.

See also official doc: https://docs.databricks.com/en/files/index.html#do-i-need-to-provide-a-uri-scheme-to-access-data