The Asrock Rack X470D4U is pretty nice, and there is a variant with onboard dual 10GbE (X470D4U2-2T) albeit only 6 onboard SATA ports and loses the middle x4 sl

The Asrock Rack X470D4U is pretty nice, and there is a variant with onboard dual 10GbE (X470D4U2-2T) albeit only 6 onboard SATA ports and loses the middle x4 slot. The base X470D4U also has the middle slot attached to the "NVMe lanes" (rather than fed from the chipset like normal) so it actually has 20 CPU-direct lanes. If you put a Noctua L9a on it, anything will be silent (although you may need to set fans manually on a server board, or use the included "low noise adapter" to drop the fan speed). That plus a 3600 (or maybe a 3100/3300X if you can source one yet) would be a good little NAS build. Has IPMI, which is nice if you will be running headless. Or if you don't care about IPMI (if it's not going to be running headless) then you can use pretty much whatever mITX/mATX board you want.