So a summary of this thread:
User A - can we have file encryption please?
OMV - Na, it's too complicated to decrypt
user B - two open source tool Encfs or Ecryptfs that just work on Debian/OMV
OMV - Can you elaborate?
user B - elaborated
OMV - Na, we care for closed source OSes only
User B - here's some toolsfor Android, Mac and Windows that use Encfs
OMV - Na, one is closed and may even require a fee.
Friends, please help not dropping on this case.