For future readers, I found the problem.
The optane m.2 NVMe is only PCIe 3.0 x2 (2 lane):
https://www.intel.com/content/www/us/en/products/sku/135581/intel-optane-memory-m10-series-16gb-m-2-80mm-pcie-3-0-20nm-3d-xpoint/specifications.html
The Supermicro x11ssm-f motherboard bifurcation is PCIe x4 (4 lane). Its BIOS won’t provide x2 or x1.