ARKit requires the usage of macOS High Sierra, because of the XCode 9 and above requirement for compiling and making changes to the API itself. So, I would highly suggest having a macOS from late 2011 or newer. I am utilizing a Mac Mini 2011 model with 8 GB of RAM, although the standard 4 GB should be plenty. Unity3D does utilize OpenCL/OpenGL extensively, which requires a GFX card capable of utilizing Metal. 2011 and earlier macOSs do not have this ability natively; this could be circumvented by having an external GPU (Radeon RX 480 is currently the only GPU supported officially for this).
With that out of the way, we can begin with installing and configuring ARKit for Unity3D on our macOS.
There are a couple of ways you ...