New motherboards supporting AMD's X870 and X870E chipset are now available, launching first on Newegg. All boards support the new AMD Ryzen 9000 Series desktop processors with the AM5 socket.
You’ll need the AMD CPU itself, a motherboard to plug it into, and a cooler. If the cooler comes with heatpaste pre-applied, like the stock AMD Ryzen chiller, then you don’t need anything else.