I recently switched from pfSense to https://www.ipfire.org and got to learn the hoops needed for PPPoE over a vlan like Centurylink needs.

In IPFire this is considered a VDSL connection and isn’t available during the guided setup. But overall it’s a pretty easy process. You’ll need your PPPoE username and password from centurylink to get started.

During initial setup select the Dialup option (even though you are on Fiber :) ).