@gskger I could. I also have a very janky solution laying around, in the form of a Mini PCIe to PCIe adapter that could replace the ProDesk's Wifi card. I could then plug in a bog standard Intel PRO/1000e Quad Nic card. Haven't got around to trying that though.

So never mind then, XCP-NG shows me the latest console output even after the VM shuts off. It clearly says "Unsupported CPU: Intel family 0x06, model 0x1a, stepping 0x5 Intel Core i7 920". Issue resolved; my hardware is ancient.

That updated my Netdata package from 1.23 to 1.26, and now the plugin is working. Thanks!