Just use OpenBSD. They are the upstream developer of pf anyway.
pfsense uses FreeBSD's fork of pf, which is years out of date. They forked in order to add multithreading, ostensibly for performance. But the diff is too complicated to keep rebasing on top of upstream, so they're stuck with a pf from 2009.
Here are a few resources to get you started. You'll learn plenty about routing!
Compared to Linux, OpenBSD is starkly minimal. It can be a little bewildering when common programs seem to be missing, but the man pages are outstanding. And the system is very simple and reliable. Config files are almost comically short. My /etc/hostname.re0 config is just five bytes: `dhcp\n`.
I appreciate pfSense offering something that's better than the average firewall, but I really wish they would just build it on top of the latest release of OpenBSD.
OpenBSD and pf really is the best. As noted above, FreeBSD has wandered off into the weeds with pf for no good reason. There have been so many improvements to pf since 2009 that I wouldn't even consider using something that old.
I used pfSense years ago when I was first learning firewalls. These days the best GUI for me is no GUI but a CLI, but some people don't want to take the time to build a firewall. Granted, once you know how to do it, it doesn't take that much time to build a firewall, but it does take time to understand what you're doing and why. But really, not that much time, considering the aggravation it can save you down the road.
pfsense uses FreeBSD's fork of pf, which is years out of date. They forked in order to add multithreading, ostensibly for performance. But the diff is too complicated to keep rebasing on top of upstream, so they're stuck with a pf from 2009.
Here are a few resources to get you started. You'll learn plenty about routing!
https://www.openbsd.org/faq/pf/example1.html
https://www.22decembre.eu/2016/05/27/openbsd-router-en/
Compared to Linux, OpenBSD is starkly minimal. It can be a little bewildering when common programs seem to be missing, but the man pages are outstanding. And the system is very simple and reliable. Config files are almost comically short. My /etc/hostname.re0 config is just five bytes: `dhcp\n`.