Adapter cards for one PCIe M.2 SSD are completely passive and work on every motherboard with PCIe. If the card has multiple M.2 slots, you need either a PCIe switch on the card or a motherboard that supports PCIe bifurcation.
I upgraded an old machine that doesn't have PCIe 3.0 or M.2 slots with a Samsung 950 Pro in an adapter card and I haven't noticed any issues - the SSD only runs at PCIe 2.0 speeds, but that's fast enough for me.
Sometimes plugging a PCIe card into one slot will cause fewer or no lanes to be allocated to another slot, so you should check your motherboard's manual before buying a new card.