Ubuntu/arm64 can run inside the QEMU emulator. You can either do this fully emulated (e.g. on an x86 host) or, accelerated w/ KVM if you have an arm64 host. This page describes how to do both.
I've chosen to describe a UEFI-based system here so I can make use of the kernel on the guest's disk image. It is possible to boot directly into Linux instead.
Note: this requires Ubuntu 15.04 or greater
Getting the bits
- Install QEMU
$ sudo apt-get install qemu-system-aarch64
Get a tianocore UEFI image. Eventually Ubuntu should provide this in a package called qemu-efi (there's one currently in Debian's NEW queue), but for now you can download one from Linaro.
- Now you'll need to create plflash