The configuration on the ISP's side was wrong; they said the connection type was PPPoA while it was actually IPoE (regular Ethernet from the box). This explains the reason I could't find the Archer's...

Today I've joined fiber connection to local ISP. I can connect to the internet from my PC, which is connected via 1gb RJ-45, and from that machine only. I cannot get internet connection in my nVidia...