To achieve this with OpenWrt 21.02.1 / LuCI openwrt-21.02 combination you have to: LuCi -> Network -> Interfaces -> Add new interface. Select the eth device of the dongle ( e.g eth1)
To verify that the device is connected, you should see something like this when logged in to the router: lsusbīus 001 Device 003: ID 12d1:14dc HUAWEI_MOBILE HUAWEI_MOBILE Since I was struggling with the last items in the list, perhaps this will help someone in the future:
