The Sony Xperia M is no longer maintained. Nevertheless a a build guide is available to build the LineageOS on your own. Be aware that developer skills are necessary to to make private builds or better check out the full maintained devices.
The Sony Xperia M is released on 2013.06 with customisation at its best. Experience the specifications and features of the Sony Xperia M featuring the Krait with 2 cores alongside 2 cameras and storage up to 4 GB.
Checkout the full LineageOS installation instruction for the Sony Xperia M!