But don't use these if your configuration is simple enough that you can manually recreate it, on the completely-impossibly-rare chance that pfSense has managed to subtly bork itself and you're switching to OPNsense to get a more reliable device....

I highly recommend implementing the firewall rules form scratch.

Firewall rules tend to aquire "cruft", especially in domestic settings, where you add rules to "fix something", and there is rarely any review of existing rules.

Personally i keep a spreadsheet of the firewall rules i need, including inter VLAN communication, with source/destination ip/port as well as a link to any article describing why this port needs to be open (like Sonos across VLANs, etc).

It sounds cumbersome, but it doesn't change frequently, and reimplementing it in a new firewall takes 30-60 minutes.