Dave, there is a spare LAN port on the WiFi switch in the den, but the hard drive has a USB connection only. I could use one of these if the computer would let me address the drive clear off in the other side of the house.

I have a peripheral adapter from when I was trying to expand the number of USB ports my laptop could use and picked up an adaptor (USB on one end, LAN port on the other, and three USB3.0 ports on the body of it). It didn't recognize anything, but maybe I need to map to them? (Separate issue.) That device won't work here but reminds me that someone somewhere will always have built an adapter to solve this problem.

More research required. For many years the go-to place for adapters and connecters and such was a warehouse-sized electronics store that closed four years ago called Fry's Electronics where you could browse up and down aisles of all sorts of gadgets and switches and cables and ports and whatnot, as well as building your own computer, set up your own home electronic systems for all sorts of things. Radio Shack closed, they had a wall of that stuff. Now it's a few places in town with a few choices or Amazon. eBay is still a source, maybe I'll look there.