In case that function is really important to you, I have got this one:
UGREEN USB C Hub Ethernet with 4K 60Hz HDMI USB C Adapter LAN with HDMI, RJ45, 100W PD, SD/microSD, 2 USB 3.0
(though I remember buying it at lower price than 50 €). All features of that hub work in LineageOS 16.0 and I thus would expect them to work in 18.1, too.
That said, performance-wise, the Ethernet adapter does not even remotely reach the advertised 1 Gbit/s: using iperf3 I measure ~150 Mbit/s up and ~230 MBit/s down. On the same network, with the same peer, I easily get 300-400 MBit/s via the Pro1's W