Very few ISPs require an actual valid username/password anymore when providing service via UFB.
These days it's tied to "Calling Station ID" which is an ID field the UFB provider "injects" into your PPPoE/IPoE request going towards the RSP's BNG. The ID they inject is based on the "port" your connection came in on. And the RSP's BNG will authenticate the user based on the CSID it gets in the initial PPPoE/IPoE packet.
So you can put "harrypotter/bollocks" in for your username/password and you'll still authenticate and get service, because the ISPs network isn't looking for that when it authenticates you.
Many consumer routers gets their knickers in a twist if you don't provide a user/pass though.