I ran into this same problem. I had vue CLI installed (3.0.0-beta.16), was following the basic steps at https://quasar-framework.org/guide/index.html.
My error was:
add:init Reasons for failure: Package @vue/cli and @vue/cli-init are not installed globally, specified template is unavailable or it failed to download.
I added cli-init via $ yarn global add @vue/cli-nit. Once that was done, re-running $ quasar init [project-name] worked for me and a new project was successfully setup.