Yes, I think that this is the USB adapter. What or where would I get the information on how to configure it on RPI 4b?

Yes, it could be so. I have two ethernet cables connected to the node (RPI4b), one in the ethernet port that seems to be working. This one is going to the router (see the diagram). The other ethernet cable is connected via a usb2 to ethernet device to the internet (my local modem/router). The issue ...

IP address : lo<LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN node default group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::/1/128 scope host valid_lft forever preferred_lft for...

Hi, I apologise if this has been addressed somewhere else. I am using the RPI 4b headless and I am running a custom Archlinux OS. I am trying to connect my RPI 4b to my home internet modem/router via a USB2.0 to ethernet connector while also connecting the RPI to a router without an internet connect...