i bet it is this issue. basically the ZuluSCSI returns values for disk geometry that somehow confuses the Solaris partition tool. one solution is to use a real SCSI hard drive and then dd it over to the ZuluSCSI once the install is completed.
https://github.com/ZuluSCSI/ZuluSCSI-firmware/discussions/122#discussioncomment-4418076
@tubetime damn, I wonder if it’s some kind of Mac-compatibility that’s breaking on SPARC?