TL;DR - www.pf2opn.com
I read about the desire for a converter here in r/homelab and on r/selfhosted this morning and I thought it would be an interesting Saturday afternoon project. I did not write this to claim a bounty.
pf2opn accepts a configuration file from pfsense in xml, does some basic sanity checks, and renders the result which you can copy. You can also download the generated xml, if you wish. The conversion happens in-memory, there are no trackers on the site, and I don't use any external services to convert your configuration. Reading and converting your configuration happens and stays on your machine. It does not cache the converted file.
I'm not running either platform in my own homelab, but I was able to find a few example configurations for pfsense and opnsense. I'd appreciate some feedback from you all as I don't think the mappings are 100% correct yet. But I think it'll spit out a nearly-usable opnsense configuration as is. However, the more sample feedback we get, the closer we can nail the conversion.
Don't forget to create backups and please don't deploy straight to prod.
I've made a tool that can convert your pfsense configuration to an opnsense configuration. It's not perfect, but it can do a majority of the legwork for you.
You can pull the site via docker:
docker run --name pf2opn -p 4200:80 -d mwood77/pf2opn
Or use it on the web here:
As always, please try the converted configuration in a test image before you apply it to a production environment. If you find any bugs, please reach out.