MacOS Ventura, 2018 i5 13" MacBook Pro, ethernet to Thunderbolt bridge, unknown state

Wired ethernet stopped working after installing Ventura. To "fix" I had to delete and manually create interfaces for Thunderbolt Bridge (connecting Display Ethernet via an Apple Thunderbolt adapter to a legacy Apple Cinema display). I also had to manually add a Thunderbolt service for a Belkin USB-C ethernet adapter connected to a port on the MacBook.

Now, the Network panel shows "Thunderbolt Bridge" "unknown state" (yellow) for the Display Ethernet, although the network connectivity is mostly fine, i.e. obtains a DHCP lease, bits are routed. In contrast the Belkin Thunderbolt Bridge always worked perfectly (green). What's the reason for "unknown state"?

BTW I rebooted enough times already.

Unlike previous editions of MacOS, hardware networking feels fragile. Perhaps things work better on Apple silicon. What happened to plug-and-play? How many people can even figure out settings like that buried in a network control panel? This used to be Apple's advantage.

Stephen