thunderbolt4 port

Since iMac's don't have a thunderbolt 4, I am not sure what you want to know.

The ethernet port on the new iMac24 is actually in the power adapter.

My new Thunderbolt 3 dock (Which is compatible with Thunderbolt 4) has an extra ethernet port. It plugs into the computer with a thunderbolt 3 cable. I would imagine that any thunderbolt 3/4 -> Ethernet adapter you get plugs into a thunderbolt port on the Mac.

Which iMac do you have?

If it is the new iMac 24 lower end model it has two Thunderbolt 3/ USB4 ports:

OWC has this:

https://eshop.macsales.com/item/OWC/TB3ADP10GBE/

but it seems a bit pricy. Do you have the Apple adapter, it is probably TB1.

I got the OWC Thunderbolt 3 dock, which includes ethernet - though I haven't tried it.