Does the PCIe x1 m.2 adapter work? Yes, but there are some downsides.
Amazon.co.jp: GLOTRENDS M.2 PCIe X1 Converter Adapter Card with M.2 Screw for M.2 PCIe 4.0/3.0/2.0 SSD (NVMe/AHCI Key M), M.2 SSD Expansion Card, Supports PCIe X1/X4/X8/X16 Lanes, Only PCIe X1 Bandwidth (PA09-X1) :
PCI-E 3.0 x1 Lane to M.2 M-Key SSD Nvme AHCI PCI Express Adapter Card PCIE SSD | eBay
Are there any PCIe 2.0 (x1) expansion cards available to add USB-C to a desktop PC? Both of my x16 slots are taken up by my GPU; I have four PCIe 2.0 (