Well, so much for that. Received my replacement CPU from Amazon and it has the same 1707 date as the original - it was just made in Malaysia instead of China. (and Chinese-made are reportedly the better overclockers)
I was sure that Amazon had previously been sold out, and that they would at least have enough turnover that a replacement would be newer than my old CPU, but I guess not.
The new one segfaults in <180 seconds now, while the old one took 30 minutes.
So if you're going to replace the CPU for this, I guess you have to go through AMD, which likely means being without a CPU for a while.
I just got a new 1700X from Newegg and I've been bitten by this as well :/
It's a major issue to me as I dont even plan to run Windows on this box. For some reason I thought it had been resolved, didn't do my research. Going to see if I can just Newegg to refund... I don't want to wait around for an RMA from AMD.
Might just get a ThreadRipper since that seems to be free of any Linux issues... though it is overkill for my needs.
edit: decided to go with TR. Just ordered a Zenith Extreme, 1950X and Noctua NH-U14S. And btw, the date code on my Ryzen was week 9... seems retailers still have pretty old stock.