https://wccftech.com/biostar-confirms-amd-ryzen-3000-support-on-300-400-series-chipset-motherboards/

BIOSTAR has confirmed Ryzen 3000 support for previous 300 (X370, B350, A320) and 400 (X470) series motherboards. Two other vendors have also confirmed support with those vendors being ASUS and ASRock.

BIOSTAR has published a list of motherboards that will have Ryzen 3000 support. AMD pledged to support the AM4 platform for the long term, and it seems BIOSTAR has also committed to doing the same for the full range of motherboards, therefore, all previous chipsets including A320, B350, B450, X370, and X470 will support Ryzen 3000.