I'm confused... why exactly do you need Windows Pro for Workstation / Enterprise for Thread Ripper 3990X?
Threadripper 3990X is a 64-Core / 128-Thread Processor... this is, at least for the moment the Maximum number of Cores that Windows 10 presently supports as a Single CPU Package.
As it stands Windows 10 supports up to 64 Cores per Processor Socket., and in fairness to Microsoft... since 2009., both Opteron and Xeon have had the largest Core Counts at 12 - 24; with Desktop being 4 - 10 Cores.
This only changed in 2017 with Threadripper Introducing 12 - 16 Cores (Consumer) and Epyc Introducing 12 - 24 Cores (Enterprise).
Mind with this said, Microsoft hasn't updated their "Differences" Table between the Versions of Windows 10 since 2016., which since then they've dropped NUMA Support as a Requirement for Massively Multi-Core Processors.
Useful, given AMD also has dropped NUMA Support outside of Epyc... likely because it was having serious issues with their Zen Architecture.
It's part of the reason why Threadripper 3rd Gen is such a substantial improvement for Desktop (Gaming) than it's predecessors.
Now it's likely that Microsoft originally wasn't expecting Core Counts to grow quite as fast as they have.
I mean keep in mind that the i9 Extreme Series only goes up to 18-Cores., while here we are with AMD mic dropping a 64-Core "Desktop" (Prosumer) Processor.
Of course Epyc also only has 64-Cores at present... ("Only" heh, imagine saying that 5 years ago) and is likely not a limitation by the Zen 2 Architecture but more as a means to not alienate Microsoft., because any more Cores and Windows 10 simply wouldn't support / see the extra Cores; while Linux would.
I have no doubt that AMD over the next few years will be pressuring Microsoft to increase their support for Massively Multi-Core Processors... as while Ryzen 4th Gen is still going to be Zen 2, thus likely still 'cap' at 64-Cores, AMD will no doubt be looking to increase Zen 3 to potentially 96-Cores.
(Remember their Roadmap has them aiming for a 128-Core CPU Design by 2024., which would be Zen 4 likely on 5nm)
AMD can (and to a degree does) support RDNA to be treated as a Multi-GPU ... but this is because they have complete control before it's interfaced with Direct3D / Vulkan., where-as for CPUs this would have to be done within the Chipset as the OS Requires "Low Level" Control.
It means getting a CPU to behave as a Multi-Processor Part, is quite a bit more technically challenging; and said feature of RDNA that I'm talking about at present isn't Consumer / Developer Exposed; rather it's just part of the RDNA ISA, which likely is being used for Liquid VR or Open XR Support... it's a bit more niche in the need for such support by Developers as there are no Graphics Core limitations set by Microsoft, unlike for CPU.
I don't really see there being any real issues for Threadripper 3rd Gen on any version of Windows 10., at least for the moment... outside of maybe being limited to Windows 10 Pro an above., but then if you can afford a $4,000 CPU; I think you can afford the extra $70 to go from Home > Pro... assuming you're not already running such.
Going from Pro > Pro Enterprise however is a much bigger leap in cost... and you'll find far less people are using such.
Mind as it stands there aren't any Dual Socket Threadripper Motherboards., so I don't see that being an issue.
At most the only real limitation you'll run into is the Memory Support; but then again you'd need a 2P / 4P Board in order to even Socket > 2TB Memory.
(Largest Consumer RAM is 128GB Sticks., and 1P Boards have 8 DIMMS)
