It is an HP Pavilion 590-p0053w with Core i5-8400 & H370 chipset. Does that mean it automatically supports CNVi for an Intel m.2 WiFi card? If not, any way to determine with a software utility whether it's supported on this particular OEM motherboard?
CNVi is supported.
A bit late to the party, I know, but I had this exact same question, and couldn't find an answer. This thread was one of the Google search results, so I figured I should update this thread, in case anyone in the future stumbles upon it like I did. In any case, I decided to just try it out myself, and the Pavilion 590 did indeed work with an Intel 9560 CNVi card.
The H370 chipset does support CNVi, so the only question really was whether or not the M.2 WiFi slot was properly wired for it. And for this particular system, it is.
(Although I did not test an AX201, my expectation is that the 9560 is the best that you can do, since the H370 predates the AX201 and I doubt that it is capable of handling WiFi 6.)