I don’t think there is an alternative Add-on to pi-hole in IPFire.
What are your looking for in Pihole? I use it sporadically on one network location, it still has the same negative effects. I think @pmueller elaborated on it little while ago.
There are few options
There is a URL-Filter but I can’t find any decent block list that works as well.
And it will only work through Web Proxy.
And if you are more Linux savvy @mutley created a script for Unbound called dns_blocklist.sh