It would be a disaster if you want to install Cloudstack onto Ubuntu 18.04 at this time (one month after its release). All the dependencies are running into incompatible issues and making it impossible to do it. However, in my situation I have to do this right now. I have read all the posts on the web, including Rohit’s blog which is not helping. Thank Robit anyway as I finally found someone facing the same problem.
But I told myself that now is 2018 and no technical issue is unsolvable. The answer is actually simple: docker. Install docker onto Ubuntu 18.04 and install cloudstack inside docker container. Use docker container as either a cloudstack management or a cloudstack agent, according to your choice.