We’ve updated our desktop requirements accordingly here.
A supported file system is required as Dropbox relies on extended attributes (X-attrs) to identify files in the Dropbox folder and keep them in sync. We will keep supporting only the most common file systems that support X-attrs, so we can ensure stability and a consistent experience.
If you received a notification, but are running one of the supported file systems, it's possible that you may have recently had a computer linked that was running an unsupported file system but have been since upgraded, or that computer is no longer being used.
Hope this helps to clarify matters!