Things tried so far.... Different network adapter - behaves the same as the on-board adapter. Different cable connected to totally different network port in a different room - no change.
---------- Results, such as they are.... Occasionally, I do get a valid IP address and gateway via DHCP, but then the adapter still can't communicate. I have managed to receive a single ping response from the gateway, out of the dozens attempted. ---------- Trying to get /var/run/dmesg.boot on a USB drive that my other non-NetBSD systems can read, so I can post.