On Macs with discrete graphics cards, Managed buffers should be used instead of Shared Buffers, however there are additional requirements to maintain synchronisation using [MTLBuffer:didModifyRange:].
However on Apple Silicon, if I force the use of Managed buffers by pretending [MTLDevice hasUnifiedMemory] returns NO, and removing calls to didModifyRange:, then the rendering is working just fine.
What's the best way to test Managed buffers on Apple Silicon where the GPU memory is unified so that I can be sure my code will work on older Macs?