I cannot help much. But have you checked with your provider that port forwarding is possible with this new fiber connection?
Here we have some providers that use something called DS-Lite. It would mean that you are “NATted” on the carrier level and share your public IP with many other customers. If this is the case you would need to get your own ip4 address assigned. I know that carriers can do this but charge for it, either by upgrading you to a different (business) plan or charge an additional monthly fee.