Linux does sound a bit intimidating when and maybe a further complication. I think I would like to get this machine up and running before going to another level.
I have been thinking out of the box
My mill table has plugs on the drive board for each axis cable .

Click image for larger version.  Name: drivers.jpg  Views: 223  Size: 155.0 KB  ID: 28835


If I were to make two leads to plug into x and z sockets and connect to x and z motors on the lathe then I should at least be able to test the axis motors .
I do have Mach 3 on the computer so should be able to call up a Lathe profile and set it up.

I might not even need to buy any gear at all. A good Yorkshire solution maybe , but must be careful not to upset the Lancashire men