I’m excited to announce an (unofficial) Ubuntu MATE 18.04 ARM64 beta image for the Raspberry Pi 3 (as well as the Pi 2 Revision 1.2 which uses the same SoC as the Pi 3).
Please note that this image is currently in beta and may be unstable. Report bugs specific to this image in the Issues section of its GitHub page, and report bugs which affect Ubuntu (or its ARM64 port) as a whole on Launchpad.
Xubuntu, Kubuntu, and Ubuntu Studio images will also be released at some point.
The GitHub page is found here.
You can download the image from the Releases section of the GitHub page, uncompress the 7z archive it comes in, and then flash it to your microSD card.
There is no way to upgrade a previous Ubuntu MATE 16.04 installation to the new image because Ubuntu MATE 18.04 uses a different kernel to Ubuntu MATE 16.04. So make sure you backup any important data if you are flashing the same microSD card containing your Ubuntu MATE 16.04 installation!
I’m hoping to get a stable release out by February 2019, hopefully earlier.