Sony may have decided to drop AOSP support for the Xperia Z, but that doesn't mean that you won't be able to get AOSP on your device. Thanks to Cyanogen you can run CM13 on the Xperia Z. The alpha version was just released for the device. The only real drawback is the fact that in these early builds the camera is not working. Other than that the build seems to be daily driver worthy. The big news here is the ability to get Marshmallow working on the device. Custom roms are good for extending the life of your phone years past the OEM's declared end of life. Head to the link below to grab CM13 for your Xperia Z.
via XDA