For modern users, the Mac OS 9.0.4 ISO is the "Golden Version" for emulation on Intel and Apple Silicon Macs.
It is the last release to officially support older Macintosh models that lack a hardware MMU. Stability Roll-up: mac os 9.0 4 iso
While it looks primitive by modern standards, Mac OS 9.0.4 introduced features that defined the Mac user experience for years to come. For modern users, the Mac OS 9