nDisplay does not run on macOS. That is a platform limit, not a setting you missed. Cluster / ICVFX / inner-frustum warp stays on Windows (or Linux).
For anamorphic or projection mapping from a Mac, treat Unreal as the content source and do the warp outside:
One output, warp in the media server. Render a flat camera (or a cylindrical/latlong scene capture) to a window or NDI/Syphon. MadMapper, Resolume, TouchDesigner, disguise, PIXERA do the anamorphic / mesh map. This is the usual Mac path.
Hardware. LED / projector processors (Brompton, etc.) take a rectangular feed and own the mapping. Unreal just fills the rectangle.
In-engine fake, single machine. A Scene Capture → render target on a warped mesh, or a post-process UV remap, can fake a simple anamorphic squeeze. Fine for one projector, not a cluster, not inner/outer frustum.
If you need real nDisplay. One Windows box in the rack. Mac stays editorial / previz.
Don’t fight nDisplay on the Mac. Decide whether you need a cluster (Windows) or a mapped single feed (Mac + mapper).