https://wccftech.com/amd-warns-motherboard-makers-offering-ryzen-5000-desktop-cpu-bios-support-on-am4-x370/

AMD has gone out of its way to prevent motherboard makers from offering Ryzen 5000 Desktop CPU support on AM4 based X370 motherboards. This was stated by an ASRock representative to customers asking if they will be receiving Zen 3 support on older 300-series boards.

It looks like X370 and the rest of the 300-series chipset motherboards would only get Ryzen CPU support up to the Matisse Refresh Ryzen 3000XT series. For those who have been wondering why motherboard makers haven't been releasing BIOS support for the new Zen 3 based Ryzen 5000 CPUs, well it looks like we have an answer.