https://wccftech.com/asrock-first-motherboard-vendor-to-officially-support-amd-ryzen-5000-desktop-cpus-on-its-x370-lineup/

So it looks like ASRock has become the first motherboard maker to officially support AMD Ryzen 5000 Desktop CPUs on its X370 lineup.

Recently, we reported how AMD's Ryzen 5000 Desktop CPUs were spotted working perfectly fine on entry-level A320 motherboards which raised questions as to why AMD had blocked support for them on their 300-series lineup in the first place. AMD has stated that due to BIOS chip limitations and the 300-series being a much older platform, they had to revise support for Ryzen 5000 CPUs for those specific motherboards but they also recently started taking a second look, raising another possibility of opening up Zen 3 support on the 300-series boards.