@Iron_Man
Did this... and it works nicely.
Last year I got a used Mac mini 2014 with 8GB RAM for a great price. Installed two left over Thunderbolt Ethernet adaptors and ProxMox virtualisation software.
This runs pfSense, next to a few small VM for automation and other stuff. I even have a VM with macOS Monterey for occiasional testing purposes on it and this all works quite well.
For pfSense I assigned 2GB memory and 200GB virtual storage. And I added a few tweaks for better performance for multi core CPU's
https://docs.netgate.com/pfsense/en/latest/hardware/tune.html#pppoe-with-multi-queue-nics
pfSense works fast. Great throughput.