Worth noting that cards such as this (with mote than one M.2 slot) require the mainboard to support PCIe bifurcation – which most old boards likely do not.
Edit: Cards with just one slot do not require this feature so you can plug them into any board that has a free PCIe slot. Unless you also want to boot from them, in which case you might need to modify your UEFI. I went that route and succeeded, but be aware of the risks involved.
Someone posted this in another thread and I was surprised to see how many well-known projects were listed among them
https://codeberg.org/small-hack/open-slopware