Hardware.Info published a roundup of the best Intel X299 motherboards
A quote from the article:
More than half a year ago, Intel introduced their Core-X processors and the accompanying X299 chip set in the summer of 2017. Since then we've done the necessary round-ups and reviews, but if you're buying a Intel high-end processor, which X299 motherboard should you get? For those who don't have time to backtrack through all of our old reviews, this article lists the best choices for those looking for a motherboard for an Intel Skylake-X and Kaby Lake-X processor.The best Intel X299 motherboards
Intel's high-end platform utilizes socket 2066, which can be found on motherboards with the X299 chipset. These X299 motherboards are characterised by many connection options, with many pci-e and memory slots. How much you can use depends on the processor you choose. The X299 chipset does not have a built-in usb 3.1 controller, so for that functionality manufacturers use additional chips, which drive up the price. This also applies to Thunderbolt 3.0: apart from a few exceptions, this interface is not found at all on X299 motherboards.