I am looking at doing a NAS build with Ryzen 3 or 5. I read that Ryzen supports ECC if the motherboard supports it. Do any ECC Ryzen Motherboards exist? According to PC Part Picker, no boards with ECC support exist.
This post provides a list.
I don't know how accurate it is or up-to-date, its dated May, so...
But on the list, which will help give you a starting point for your search:
ASRock -All x370 support [Not confirmed to actually run in ECC mode] ECC unbuffered [Unconfirmed Windows support, Claimed support in Linux >= 4.10]
X370 Taichi -Linux 4.10 ECC support listed on QVL
X370 Killer SLI/ac
X370 Killer SLI
Fatal1ty X370 Professional Gaming lists 3 ECC chips in QVL
Fatal1ty X370 Gaming K4
ASUS -Support for ECC unbuffered
PRIME X370-PRO -3rd party claim -3rd party claim 2 Transcend ECC chips listed on Official QVL