I have just now tested my 3700x CPU with the currently available BIOs… did not boot. Emailing asrock support now.
if you are okay with a 2nd gen ryzen on this motherboard for now… then you are golden…
if you want 3rd gen ryzen on this motherboard right now… it is not working.
This was taked about in the X470D4U megathread. The issue is with a broken random number generator due to bios/agis version that is required by systemd in contemporary versions of Fedora.