If you just had a peek at the ASUS Ryzen 3000 compatibility list you will have noticed that A320 motherboards are not updated for compatibility. ASRock however also updated their support pages and it seems AMD Ryzen 3000 chips could be compatible with their A320 motherboards.
All ASRock motherboards receive a BIOS update (AGESA to 0.0.7.2) that presumably supports Ryzen 3000 processors. You can check a list is on the ASRock support pages here and that page shows models for A320, B350, X370, B450 and X470 chipset getting the very same AGESA 0.0.7.2 firmware update.
I do want to note though that these firmware updates can go two ways, they probably can support Ryzen 3000 processors. However, it could very well be that the new support is intended for just the 3000 series APUs, and these are based on the Zen+ (2000 series) architecture.