I'm looking to pick up a few enterprise NVMe SSDs, but they're in U.2 form factor and I don't use any backplanes. Are there any issues if I just picked up a passive U.2 to PCI-e adapter instead of using a NVMe HBA with retimer chip? Some example I'm thinking about:
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NeweggBusiness - StarTech.com x4 PCI Express to SFF-8643 Adapter for PCIe NVMe U.2 SSD Model PEX4SFF8643
Buy StarTech.com x4 PCI Express to SFF-8643 Adapter for PCIe NVMe U.2 SSD Model PEX4SFF8643 with fast shipping and top-rated customer service. Once you know, you Newegg!

U.2 NVMe SSD SFF8643 to SFF-8639 NVMe U.2 with Cable PCIe x8 Dual Port Adapter | eBay
2x SFF8643 to SFF-8639 Cable. 1xANU22PE08 PCIe x8 Dual Port Expansion Card. Note: The motherboard PCIe slot needs to support the split function. LED indicator: Yes. (Does not contain SSD/Solid State Drive).
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