Keywords Instead of Albums With iCloud Shared Photos
[There’s] no way to share albums in iCloud Shared Photos. All the photos can be shared, but the concept of an album is currently limited to a single Apple ID.
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Every item in the Photos library can be assigned a keyword, and keywords are synced across iCloud Shared Photos. So if you want to collaborate with other members of your iCloud Shared Photo library—or even if you just want them to be able to view the curation and selection—you can do this by selecting all the photos you want to collect and assigning them a keyword.
I'm the author of the free open source tool, osxphotos (https://github.com/RhetTbull/osxphotos) which provides several tools for working with Apple Photos. I've developed a workflow to sync albums between iCloud shared libraries using the `osxphotos batch-edit` tool.
If you install osxphotos and run the command periodically on each user's Mac, it will create keywords in the form of `album:Folder/Subfolder/Album` for each photo in an album. Then it will find any such keywords that already exist and add each photo to the appropriate album, creating folders and albums as necessary. You must select the photos to apply this to (e.g. all those in an album or all those in the shared iCloud library). This is a bit of a hack but it works and is "hands off" after running the command.
osxphotos batch-edit --verbose --keyword "{album?album:{folder_album}}" --album "{keyword|filter(startswith album:)|sslice(6:)}" --split-folder "/"
This command uses the osxphotos template language to create keywords if an album exists and then uses the template language to extract the folder and album names from the keywords which are then used to create the albums (if needed) and then add the photos to the appropriate albums.
There is a limitation that if you remove a photo from an album, the keywords are not removed nor is the photo removed from the album. AppleScript, which osxphotos uses to add photos to the album, is not able to remove photos from albums.