As you may know, Ubuntu Touch, which is the mobile version of Ubuntu, is available by default on Bq Aquaris E5, Bq Aquaris E4.5, Meizu MX4, but officially supported on the Nexus 4 and Nexus 7 devices.
The Ubuntu developers are currently working at implementing encryption on Ubuntu Touch, but the new feature will be most likely implemented after the release of Ubuntu 16.04 Xenial Xerus.
The official announcement:
“We have high-level plans to support encryption of user data. It isn’t clear at this time if that will be based on LUKS, eCryptfs, or ext4/f2fs encryption. We’ll know more once we’re a bit closer to implementing the, feature but there is currently no set timeline,”
The main problem is that the encryption impacts on the overall performance of the device, and this is the main reason why mobile operating systems do not have this feature implemented. Android 6.0 Marshmallow received encryption, but only for the /Data folder and the SDcard.