It turns out there is a less drastic way to do that.. the thing it’s blocking is multicast traffic, which is traffic to 188.8.131.52 on port 5353.
If you could find a way to enable just that traffic, it would work.
Sadly, I found Guarddog to be so byzantine as unusable, at least for me. I find it curious that one could build a graphical interface more complex and unintuitive than the command-line commands it replaces. IP tables is straightforward and clear to me. Maybe it’s just me.
But if you could find a way to enable that traffic, it would work.