I think I heard that the latest 'rclone' now, finally, support iCloud ... but I think there is an issue there because you can't sync full quality / RAW photos to icloud, can you ?
replyrclone has support for iCloud Drive, but it sounds like you are talking about iCloud Photos, which is a different service.
replyThis project lets you download from the latter: https://github.com/icloud-photos-downloader/icloud_photos_do...