Sony’s Marshmallow beta program was announced a little over a month ago and since then, there hasn’t been much activity until last week when the Xperia Z2, Z3 and Z3C all started to get the Android 6.0 OTA.
The build number for this update is 23.5.A.0.486 and it brings all the new features found in the Z5 build of Marshmallow. The most significant is actually a direct port of the Camera 2.0 interface found on the Xperia Z5. Due to Google’s implementation of Doze in Marshmallow, Sony was required to remove Stamina mode from all its Android 6.0 builds.
Do remember that while everything may seem fine, Sony has still labeled this as beta software and as such, it is not intended to be used as a daily driver. However for those that are keen on trying this out for themselves, you can follow Xperia Blog’s tutorial here.