CyberDuck is a swiss knife tool for various cloud storage providers. It supports FTP, SFTP, WebDAV, OpenStack, OneDrive, Google Drive, Dropbox, etc.
After starting Cyberduck you set everything as usual to access the S3 object storage, in addition “More Options” must be clicked
The name of the bucket is added to the “Path” field. Then just click on the “Connect” button.