Looking under View > Show Hidden Devices revealed the Realtek driver, greyed out, not recognised by Windows as a current device. Updating the driver didn't recover it. Uninstalling it removed it completely and it didn't come back when clicking Scan for Hardware Changes.
The fix was to reload the driver from the latest HP download (transferred via USB flash drive from an online computer)
Realtek Ethernet Controller Drivers version 10.32.1206.2018, dated 9 Apr 2019, at time of writing this.