I am tempted to build something similar but AMD's wishy-washy ECC guarantees as well as Linux-specific issues make me unsure.
ASUS PRIME TRX40-Pro motherboard
8 sticks Kingston KSM26ED8/16ME (16GB, 2666Mhz DDR4, ECC)
Dual boot Windows 10 / Ubuntu 18.04
2x Samsung EVO 970 NvME M.2 1TB SSDs in RAID0 configuration.
Running in a Coolermaster Cosmos case with a stupidly big air cooler at the moment, to be replaced with a decent liquid cooler (it works, the Cosmos is a huge case because it had to be to hold a hacked Supermicro dual Xeon server board in it before (I really wanted ECC for my workstation))
nVidia 1080Ti+ GPU.
The ECC is detected and claims it is working although I've yet to see it correct an SBE. I haven't been running non-stop memory tests either though so.
I may end up removing the Linux partition since WSL2 works so well on this box.
BTW, Century Micro has the only unbuffered ECC modules at 3200MHz native speed (at least that was the case on the 39x0X release day). I don't know if they can be sourced outside Japan, though.
Fun story, I actually botched my order and got 2666MHz ones... but on closer inspection, it turned out the chips on the modules were actually native 3200MHz ones. With the SPD EEPROM saying they are 2666MHz. So I ended up overclocking them at their actual native speed. And I tweaked the timings to be a little shorter than what the 3200MHz modules were advertized for.