Based on my experience, I was able to get this motherboard to work with ECC ram:
ASRock B650M-HDV/M.2 Supports AMD Socket AM5 Ryzen 7000 Series Processors
But nowhere does it say that this board supports ECC. I was using a Ryzen 7700x and when I put ECC ram in, the TrueNAS GUI said it was ECC and I was able to use MemTest86 that you put on a USB stick to truly test if it was actually in ECC mode and it was.
In other words, I think it SHOULD work, but you might just need to test it and return it if it doesn’t or research some more.