Not family with that model specifically but you should be able to. I used to have a setup like this but moved it back to keep a separate subnet on my home network.
Discussion
Found this thread, not sure it's the best option. It's probably possible with some tinkering and it's really cheap for what it is. $53 shipped on the listing. But I don't think I want to tinker with it that much.
https://forum.netgate.com/topic/154974/pfsense-on-watchguard-m270
Yikes yeah that does look like a bunch of work. I used to work in networking and was often allowed to take home devices from customers that no longer needed them and sometimes piggyback off my company’s licenses. I have only ever done a pfsense device connected to the WAN as a VPS and whatever I was using did not require a license or significant mods.