Thanks for your follow-up. The dongle works on the Pi, and in fact , has worked on any system that i have, for various reasons, tried it on. As for remote admin, I use Jump Desktop connecting to TightVNC. Jump Desktop connects to my Mini, 2 PCs, 3 Pis, a Ubuntu server, and a virtualized Win10 and a virtualized FreeNAS, both running under Ubuntu. Top shelf program; couldn't function without it.
Since I have your ear - it seems that Linux MC has no server? Is this true?
I'm not sure I understand what you mean? In terms of actually functioning as a server, Linux MC works as a media server and has almost similar server functionality to the windows version (that's an area where it's close to feature parity, except for live TV). It doesn't have a tray widget if that's what you mean, but that's just cosmetic. If you start the linux instance with the "mediaserver" flag, it will start minimized, use less memory, and not throw any modal dialogs that would hang the UI. It just won't give you a pretty tray icon, but works perfectly as a server.
Consequently, I run the MC server in the Win10 vm.
Unless you need live TV, you don't need to do this, see above.
MC runs and connects to my NAS without any problems. However, I can't connect to the MC server, running in the vm machine, from another MC. I use the access code that the MC server supplies and the MC client uses it to try to connect, but it can't find the MC server, although it seems to know its address. I can't positively confirm this since the message addressing this is truncated in the MC messagebox. Guest connecting to outside world - OK; outside world connecting to guest - not so much. I know it has to due with the fact that while my network ip is 192.168.0.xxx, the vm guests run on 192.168.122.xxx. This is recognized by the MC client, but it can't connect because it seems to be a different network. This can be addressed, but requires some research on my part.
I don't know what kind of virtualization solution you're using or how you've configured it, so I can't give very detailed advice, but it sounds like the problem is that you're using "NAT" style VM networking. With NAT networking, the host for the VM acts like a router/firewall for the VM, so the inability of programs outside the VM to reach the VM is by design. It's not just that it's on a different subnet, the host is actively blocking traffic to the VM unless you enable port-forwarding or address translation deliberately. Most VM solutions offer other networking modes than the "NAT" mode; for example, virtual box offers a "bridged" mode which effectively just makes the VM another "box" on your home LAN. It can then see and be seen by everything else on the LAN, etc. That kind of configuration is better if you're uncomfortable doing port forwarding.
But you really may not even need the VM; the linux version works fine as a server. Just leave the program minimized, or start it with the mediaserver flag.