The coreboot support for Ultra 40 M2 was for Fam0Fh processors only. As support for Fam0Fh processors was removed so was the board support.
I've never got around to upstreaming my Fam10h port.. I could probably push it out somewhere if someone wants to polish it up. I refreshed it only a couple months ago, and it pretty much works for me.
Only reason there wasn't a more recent board status is because I had the Fam10h processors in my system, and didn't feel like swapping in the K8 ones just to test. I expect the K8 support would have been removed even then.
Jonathan Kollasch