I know at least Egnyte (https://www.egnyte.com/) offers folder permissions, and has clients on Windows, Mac, Android, iPhone and iPad. The Linux client is available on some NAS devices and also as a VMWare appliance.
Disclaimer: I work for Egnyte.
Disclaimer: I work for Egnyte.
But having said that, we do provide WebDAV API. Every modern OS I know of, including Linux, can mount a file system over WebDAV. It is not very efficient, and doesn't have all the features you would get with a client, but at least you have access to your files.
Some people actually prefer to use only WebDAV, because that way as soon as you cut network connectivity the files are not accessible (security feature).