ASRock AB350 Pro4 does support ECC with UEFI Ver 4.70 : r/Amd
Build a PC for Motherboard AsRock AB350 Pro4 (sAM4, AMD B350) with compatibility check and compare prices in France: Paris, Marseille, Lisle on NerdPart
BIOS update and M.2 Question AB350 pro4 : r/ASRock
ASRock AB350 Pro4: A Decent, Linux-Friendly Ryzen Motherboard For As Low As $69 USD - Phoronix