I'm thinking about moving my calendars and contacts to "the cloud". For privacy reasons I'll only consider end-to-end encrypted providers. Such exist.
Obviously (?), full end-to-end encryption and, say, serving CalDAV are incompatible requirements. The best I can hope for is to store the information as synced files which are read and written locally. Let's assume a single-user environment for simplicity, i.e. we don't have to care about concurrent updates to these files.
What are existing solutions for this? I'm interested in clients (or plugins for software) on Android and Linux.