@justincm , welcome to the Community.
Here is what it states in the Product Specifications, in the section titled "Expansion slots, for the M.2 socket: One M.2 socket 3, key M (for SSD card PCIe x4 Gen 3). I believe that the Gen 4, M.2's would be backward compatible, but you wouldn't gain all of the benefits of the new generation.
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I am not an HP Employee!!
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