I am trying to run X from within a systemd-nspawn container - this is something I had set up and was running successfully about three years ago, but something seems to have changed in the meantime and I am not able to recreate this.
I created the container and installed X related packages following the wiki article, and was able to boot into my container and create an unprivileged user. The script I am using to boot is (modified from my container of three years ago):
xhost +local:
Do you want to run a full X server inside the container or just X applications? I'm confused by your use of `xhost +` here. A full server needs to be started on a real console, so that might not be possible at all in a container. But you're passing /tmp/.X11-unix/ and setting DISPLAY, so you might only want to run X apps? In which case you don't need startx. -- damjan