Just replicating the relevant parts for anybody interested.Reddit r/AMD AMA (Lisa Su, Robert Hallock & James Prior)
This is what I can find. Just search for ecc on the thread
A: AMD_Robert Technical Marketing
ECC is not disabled. It works, but not validated for our consumer client platform.
Q:
What does "validated" mean in this context? What sort of stumbling-block does that represent to those who want ECC? Will it still be possible to build ECC-enabled servers with consumer-grade (and consumer-price-range) hardware on the Ryzen platform? There are a significant portion of users who want ECC for their NAS/Homelab setups.
A: AMD_james Product Manager
Validated means run it through server/workstation grade testing. For the first Ryzen processors, focused on the prosumer / gaming market, this feature is enabled and working but not validated by AMD. You should not have issues creating a whitebox homelab or NAS with ECC memory enabled.
Q:
So the Ryzen has full ECC support, if I install a ECC memory, it would work in ECC mode, not non-ECC mode?
A: AMD_james Product Manager
yes, if you enable ECC support in the BIOS so check with the MB feature list before you buy.
Q:
Thank you for the answer! So, the AM4 platform / socket theoretically has everything to fully support ECC and it's only up to mainboard manufacturers. Is that correct?
A: AMD_Robert Technical Marketing
Bingo.
A: AMD_james Product Manager
Yes, it's down to BIOS support.