I just put in a single 16 GB of ECC RAM right now and will add more over time as the machine gets set up with VM's etc.
So far the mainboard has been great. I think BIOS reset itself once, but that was with a lot of testing with the M.2 adapter and riser cables etc., so not entirely sure what happened.
Server 2016 (Essentials) and Server 2019 are running good on it so far. Needs GPU & network drivers (which are on the SM site), and there's a bunch of unknown PCIe devices, but that doesn't seem to impact anything.