I have 2 Supermicro H13SAE-MF with Ryzen 9's and ECC UDIMM RAM. It's not registered or LR ECC RAM like a mainstream server though, and not as fancy as Chipkill-like ECC systems. This particular board also accepts EPYC 4004 / 4005 series. I'll probably replace the Ryzens with EPYC 4585PX once they get old enough and cheap enough on the secondary markets. These boxes are 100 Gbps network test nodes.

(I'm currently in the midst of refanning my CSE847-JBOD with bigger, quieter fans and swapping PSUs.)