The German branch of Seafile:
https://seafile.de/en/products/I switched all my data (about 250Gb) to them from Dropbox a couple of months ago and it has worked out well enough.
Features:
- servers not based in the US
- encryption
- privacy
- open source (thanks lima)
- multiple libraries (like multiple separate Dropbox folders)
- nice file manager for unsynced (parts of) libraries
- price
- payment options (Bitcoin)
- supports more OSes
- one can run one's own server
Cons vs Dropbox:
- syncing problems not always obvious
- some UX issues
- photo support
- selective sync cumbersome (if not using libraries)
- no LAN sync