Ah yeah - always a good idea to verify support on the motherboard. I think AMD mbs are usually better on the bifurcation front than Intel ones.
The Startech card I linked is backwards compatible with PCIe 3.0 M.2 NVMe cards, they mention that they’ve tested with Samsung 970 EVO for example, so you can still fill it up with older, cooler M.2 cards even if it supports PCIe 4.0.