Save on iPhone
Open the public work in Safari, use Share and Copy Link, then paste it into the downloader. Choose a format after the source is resolved.
For converted formats, keep the tab open while the file is prepared. Safari may ask you to confirm the download. You can find the saved file in the Files app under Downloads.
If a media preview opens instead, use the share menu and Save to Files. The exact available actions depend on the browser and the media format.