If you are planning for 5950x get a 500 series chipset Mobo specifically the X570
Question to keep in mind while purchasing Mobo;
*Is there enough usb port?
*Is there wifi?
*Hows are the VRM's if you plan on oc
*Enough expansion slots?
*No. of M.2 if yes pci e or sata? Maybe gen 3/4 for the nvme ssd
*Enough ram slots??
*Any brand preferences
*And most importantly if you like the look of it?
The new 5950X is going to fit into the existing B550 and X570 motherboards - I would suggest looking up reviews of X570 boards (no point skimping on a motherboard with that CPU!).
The main points to look for;
Strong VRM performance (this is the circuit which feeds power to the cpu - better VRM's on the board mean lower temps and more overclocking headroom)
4 Memory channels (some compact motherboards only offer 2 memory slots to save space) - although probably not an issue when looking at X570
Other than that, it's really down to what features you need as different boards offer many different options such as
Different numbers of PCIe expansion slots, as well as slots for adding in NVME drives
Different numbers of Sata ports
Varying configs on USB IO (e.g. some boards offer extra USB 3 or USB C headers for the case and so on)
Networking options - some boards offer integrated Wifi, Bluetooth as well as different wired networking ports like 1gig, 2.5gig and so on
Additional RGB headers and Fan Connectors
The Hardware Unboxed youtube channel have a pretty comprehensive set of reviews on the range of available X570 motherboards.