Folders in iCloud Drive change their permissions
I had the same problem, trying to run a server as an unprivileged user that needs read access to Documents, while Documents is in iCloud Drive. Normal UNIX file permissions didn't stick. I solved it by using  ACLs to grant access.
chmod +a &quot;_www allow list,search&quot; Documents
In this example _www is the unprivileged user your server is running as. Use ps axu to find out what user that is for you.
The folders inside Documents should work like normal with UNIX file permission bits, so you only have to do this for the Documents folder itself.
For more info on ACLs, see here here and man chmod.