Also happy to help. I’ve modded on Reddit a few times and agree with light touch to avoid all the dramatic junk.

You cannot just buy any SFP module and have it work. Most ISPs deploy a “special” (at least compared to normal point to point fiber links) that lets them serve multiple customers out of one port in their office. This is called a Passive Optical Network and requires specialized modules on both ends. There are ways to make a specific SFP work as an ONT and by cloning certain identifiers from the ONT to make the ISP think their box is still there.

This is a lot of effort and from my research, could stop working randomly in some cases.