I'm not sure how many, but Dell has at least three in the PowerEdge line and they've been announced and available for a while. One of them is a 1U single-socket system with 32 cores, 64 threads, and up to 2TB of RAM.

https://www.amd.com/en/campaigns/amd-and-dell

https://www.dell.com/support/article/us/en/04/qna44314/dell-...

https://blog.dellemc.com/en-us/poweredge-servers-amd-epyc-pr...

http://www.itpro.co.uk/server-storage/30799/dell-emc-powered...