I watched HardwareUnboxed X870 roundup and all Asrock boards + Gigabyte Aorus Master were able to fully use ECC memory.
X870 Pro Art even explicitly states it support ECC UDIMMs but strangely it failed in ECC test in above video. There is thread on this forum about X870 ECC support and member wrote there that we dont know how Hardware Unboxed ECC verified if motherboard fully support ECC memory so its unknown how reliable their results are.
How is ECC on Z890? No Z890 officialy supports ECC but as we saw in X870 Asrock and Gigabyte boards, they do support ECC even if they dont advertise it. Did Asrock enable ECC on their Z890 boards too?