Software to allow XP to make SMB2 connection to file share

Unfortunately the answer is no.  SMBv2 under XP would require replacing parts of the Microsoft TCP/IP messaging stack.  XP's system file consistency checker would not tolerate this even if a third-party replacement was available.  Only Microsoft has the encryption keys necessary to replace system files properly, and they declared XP dead some years ago.

You might be able to migrate the XP applications to a 32-bit version of Vista.  Go to your local computer recycler, say "I want a 32-bit Vista machine" (preferably from Dell, as they are easier to support) and it should cost no more than $20 to get one to play with.

Sadly Dr. Klahn is correct and the only other answer that usually appears in questions like this here is to stop using XP if you need secure networking on that machine.  I still support some very old XP legacy systems that run tools and equipment that there is no new software for. Those machines are not on the network (or blocked by the firewall) because of the SMB1 security issue. We use “sneaker net” (USB drives) to put files on those machines when needed.

We even looked into virtualization hoping the host machines networking might add the security layer we needed (like XP Mode in Windows 7), but  the VM does not appear to pass that traffic through more secure layers.

I fully agree with the above and you need to dump XP as dead, gone, major security risk, and no more software for it.

Please move up to a more modern operating system.

If you have software or equipment that will only run on XP, please ask your accountant about Amortization and then move up.

Sometime XP is still used in controller stations driving manufacturing/medical devices...
they are at time tied to the Vendor equipment. ..

The VM is an intereting IDea, the difficulty it has to be accessed by the HOST and shared to the guest XP system.

The complete scenario once included could be the course the prior three suggested, move to a more modern system.
Not sure making the effort to go to Vista( though not sure there was a direct upgrade path from XP to vista)
Out of my own curiosity. one can. BUT I would think this is an undertaking that could ....
https://support.microsoft.com/en-us/help/931226/how-to-upgrade-from-windows-xp-to-windows-vista-by-using-the-upgrade-v
presumably after vista, one would move to windows 7 via upgrade as the next logical step?

Main question implied, is what is on this system (XP) that kept it around for the past some 4 years.

You're using Nutanix for file services? That's unusual. If you really need XP to access some files, move the files back to a Windows fileserver (VM) or a Samba share that you can enable SMB1 on.

The XP systems are used with custom software in industrial devices that cannot be migrated quite yet, but we are aware of the risk.
Since there is hardware dependency we were also unable to go to VM.

I wanted to make sure it was the only option before taking action

You can't use DFS Replication between Windows and non-Windows filers. You can robocopy data over, but the point is that you need to get data onto a filer that speaks SMB1.