Installing Ubuntu 18.04 arm64v8 on Raspberry Pi 3

I believe for bluetooth support, you can use the packages from raspbian, http://archive.raspberrypi.org/debian/pool/main/p/pi-bluetooth/ (some other packages may be needed). This is how the Ubiquity Raspberry Pi image works, albeit for Xenial armhf.

@dheera Ubiquity Robotics maintains a Raspberry Pi Image with Ubuntu 16.04 + ROS Kinetic available here https://downloads.ubiquityrobotics.com/pi.html. You might be interested.

Rohan
Ubiquity Robotics