Someone on the internet said, make a new Location. So I created a Location, called Docked by copying that. Every other device in the house including two MBPs connect fine to all three networks in the house.
Nothing changed. The PROBLEM is that even when I DO disconnect the wired network, the wifi still does not connect.
The other thing I noticed is that when the the computer is connected to a wired network, the “hostname” changes. I don’t know why this would matter.
~ % hostname Marvin-MBP.local ~ % hostname Marvin-MBP.home ( hostname when a wired network is connected)
The wired connection is accomplished with a Anker “Power Expand 5-1 USB C hub” which requires no driver, and seems to work fine. Some combinations of reboots and creating and deleting “Locations” seems to (maybe) fix things for this MBP, until I reconnect it to the wired network, at which point the problems recur.