At least as of the last major macOS release, that will not work, because the PCIe LSI SCSI HBA driver doesn’t have the extra stuff needed to support external PCIe.
It’d be a pleasant surprise if Apple implemented that for macOS 26 but I wouldn’t hold my breath.
Interesting... What bothers me is that you'd think that with Mac Proc M2 having advertised support for "storage" cards and lots of PCIe slots, at least some SCSI HBA's would have drivers?
It’d be a pleasant surprise if Apple implemented that for macOS 26 but I wouldn’t hold my breath.