Setting up fiber PPPoE connection

My current setup uses an ONU to bridge the ISP's fiber to my SOHO router, which handles the PPPoE connection.
In addition, I had to enter the GPON SN and the VLAN ID to connect the ONU.

I have a mini PC with an SFP+ port, a "Mellanox ConnectX-3" controller, and I wanted to plug it directly into my ISP's fiber. However, I am not very familiar with OpenWRT and I'm unsure if that is feasible.

Do you have any tips or tutorials to share regarding this?

There’s one on YouTube called van tech corner (don’t have the url just now). He shows different types of setups with sfp including pppoe.

Maybe that helps.

I don't know what it is like where you are but the ONT in New Zealand is part of the providers network and they will not allow you to connect direct to the fiber as it is classed as a layer 2 network and is protected and encrypted.

Company's can request direct to fiber networks between buildings and offices (at great cost.).