Updating kernel to 4.8 fail

Trying to get kernel 4.8 going with:

sudo apt install --install-recommends xserver-xorg-hwe-16.04

Failed on RPi trying to update-initramfs.

Errors were encountered while processing:
linux-image-4.8.0-36-generic
linux-image-generic-hwe-16.04
linux-generic-hwe-16.04

Anyone have success with this?

Rapsberry pi support is not completed on upstream kernel !
Ubuntu mate and other Ubuntu flavors use downstream kernel from raspberry pi fondation.
So you cannot use hwe kernel. The tool to update kernel for rapsberry pi is rpi-update but don’t provide any hwe kernel.