I have an iMac running OS Catalina, although the same issue was there before the recent OS upgrade
I have a new plusnet hub one router, with an ethernet directly to the iMac
In network settings, the wifi works fine, but the ethernet has the following message and won't connect:
"Ethernet has a self-assigned IP address and will not be able to connect to the internet."
I've tried up working through the network settings options: made sure it is "configure IPv4", using DHCP, renewed DHCP lease, tried setting up a new location (default one is automatic) and renewing DHCP lease on new location - no effect.
I'm coming to the conclusion it is a router issue. Any ideas?