I can live with the situation, but it is inelegant. There was a time when ethernet through USB worked intermittently but for the last few weeks (with no new software installed), it hasn't worked at all. Assigning a fixed IP address rather than DHCP (something suggested in posts late last year) didn't help either. I have tried disabling or uninstalling everything that starts up on log-in including prime suspects lime me Intego firewall, all to no avail. When I go into safe mode internet access is perfect with a USB to ethernet adapter. It just is kind of clunky for travel, etc. WiFi works fine for everything, and when I default back to an old Thunderbolt 2 - ethernet dongle, connected to another thunderbolt 2 - thunderbolt 1 dongle that works fine too. However, all connections to the internet time out. I've tried multiple brands with different chip manufacturers and the same thing happens: network settings recognizes the USB ethernet adapter, assigns it an IP address and it works fine for all LAN activities. Everything works flawlessly except that no USB ethernet connection will work properly. I have read posts about this several months ago.

Use a usb to ethernet mac