It's possible, currently I have a GPON-ONU-34-20BI connected to my PFSense router, the optical fiber is directly connected to this GPON which is inserted into my PFSense router on the integrated WAN card. The Livebox is in the closet (and between us, I'm glad about it!!), and I control my entire apartment (servers, wall socket, Wi-Fi, IoT, ...) with this PFSense router (I'm waiting for XGS-PON to upgrade to a higher model

. The Orange WAN is in DHCP V4/DHCP V6 and my different VLANs are in static V4 and track interface to retrieve an IP delegated by Orange! All of this with an average uptime of 100 days (I only reboot the PFSense for updates) and a constant throughput of 1Gbps/1Gbps.
Can you just confirm which version of PFSense you have as well as the Livebox model you have (v5/v6)? I'm going to make a little guide on my Git next week, there's a lot of information to consider but I've configured most of the points to be modified by script so it should be pretty straightforward!