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For which platform, and what will you be doing with it?
If it's for a budget NAS, then a 4-port HBA PCIe card will do the trick on almost any motherboard.
If you want to build something a bit more fancy, then a server-grade board with out-of-band management like these will give you a lot more options:
https://www.asrockrack.com/general/productdetail.asp?Model=ROMED6U-2L2T#Specifications
Any recommendations for a (mATX) motherboard that has 6x SATA ports and 1x M2 that isn't ruinously expensive? Lots have that combination but using the M2 disables a couple of the SATA ports (which is generally in the small print in the specs somewhere).