Hi folks!
We're using a small piece of code to help us to convert from pfSense to OPNsense XML config file. It's still in a beta stage, but we're achieving good results with it.
There are known issues that should be corrected/improved. Contributors are very welcome! ;)
https://github.com/juliocbc/shelland/blob/beta/pf2OPN-config.sh (https://github.com/juliocbc/shelland/blob/beta/pf2OPN-config.sh)
Tested with XML files from pfSense 2.1.X and 2.2.X versions.