No Ethernet

A few days ago we had a pretty vicious storm. Some bad electricity appears to have gotten through the UPS and into my mini (2018 Intel-based). In the process of getting things back in order, I noticed that the preference pane System Information/Network said that the Ethernet cable was disconnected - it wasn't. After I applied the 12.6.9 update to Monterey, which fixed a different issue, any reference to Ethernet on that pane was gone. I've tried a different cable, I've made sure I was using a port on my router (Airport Extreme) that worked for another device, I've reinstalled Monterey, and Apple's Diagnostics (pressing "D" while starting the mini) returned "No Issues Found". At this point I feel like I'll be replacing the mini sooner than I'd intended, but can anyone suggest something I should try?

srb