I sincerely apologize for sending you guys so many notifications, but I think this ought to be emphasized.
Apple plans for hardware features several years before they’re implemented. Apple may have added atomic UInt64 min/max precisely to get Nanite running on M2. In early 2020 they saw the UE5 demo and wanted AS to support it for the planned “Metal/Macs for gaming” focus. Then relations with Epic derailed (late 2020) but the chip design was already established.
This explains why they strangely added only one 64-bit atomic instruction when they could have added all of Shader Model 6.6 functionality.
Until further notice, all information about the Nanite on Mac/iOS investigation will be posted on the ue5-nanite-macos repository’s README.