How to run Unity 8 on Ubuntu inside of VirtualBox?
Solution 1:
You can't run neither mir nor wayland on virtualbox. Maybe in the future... See also the links: https://www.reddit.com/r/Ubuntu/comments/3v2tof/unity_8_in_virtualbox/, https://bugs.launchpad.net/ubuntu/+source/mir/+bug/1366805, https://bugs.launchpad.net/mir/+bug/1118903.
EDIT(2017-13-01): You can run wayland inside virtualbox now. I have successfully launched a plasma wayland session on KDE Neon Developer Edition Git Unstable with virtualbox 5.1.12. I'm not sure about Mir. I will have to test some ubuntu 17.04 Alpha release to find out.