Well only because I did not found Prometheus anywhere here, I add the request for a Prometheus Export for ipfire.org firewalls, basically it*s a JSON webservice listening on a port (default 9100) with a scraper before (how to develop).
P.S. No this is not an promoting ad for Prometheus. I am just using it for my own servers and would be happy to include my ipfire.org firewalls somehow.
P.S.S. I would contribute the development with a small bounty, maybe we find some more conributors?