[guiambros]

Try compiling pfSense.

No, here's an even simpler task: try compiling packages for pfSense.

The clowns from Netgate made it unbelievably difficult, for no good reason other than being antagonist to the open source community.

[SpecialistK]

Meanwhile, I've never tried building OPN but it looks well documented and can be added to a vanilla FreeBSD install. https://github.com/opnsense/core