Sorry, my post was maybe a little bit ambigous.

My adapter (part of a multiport adapter) had the initial id of 0bda:8151

Port 1: Dev 3, If 0, Class=Mass Storage, Driver=, 12M
ID 0bda:8151 Realtek Semiconductor Corp. RTL8151 Adapteon Business Mobile Networks BV

After issuing the modeswitch ...

for 0bda:8151 and 0bda:8152

see
https://forum.manjaro.org/t/solved-ethernet-not-working-via-multiport-adapter/41773/9

sudo usb_modeswitch -v 0bda -p 8151 -V 0bda -P 8152 -M 555342430860d9a9c0000000800006e0000000000000000000000000000000
sudo usb_modeswitch -v 0bda -p 8152 -V 0bda -P 8153 -M ...