TinkerTry writes up a few M.2 NVMe PCIe adapters
No M.2 NVMe support built into your motherboard? No problem, check out one of adapters TinkerTry has played with.
Such adapter cards pass signals from your M.2 NVMe device right through to your motherboards PCIe slot, with no speed degradation. You can see these simple wire traces in the close-look video that's featured below, so there's no special drivers needed. Modern PCs and servers simply "see" the NVMe drive, whether it's in a motherboard socket, or installed in any of these adapters. A nice perk, if your system can boot from NVMe, it can likely boot just fine from any of the M.2 NVMe devices mounted in any of these cards.