I've known a few people into black powder guns and cannons. It is a fun hobby for them. One of them got into it by way of model rocketry, the rest were folks who were generally into "mountain man" era skills, technology and reenactment (for history and fun, not prepper illusions).
There was also a tradition at our high school to shoot off a cannon each time our football team scored a point at home games (just the powder no projectile).
I'm now curious if one could license one here. It doesn't _obviously_ fall into any of the categories that would make it prohibited (as opposed to merely restricted), and it's not like it'd be very useful for criminal purposes, but it might be hard to sell the gardai on the idea that it was essential for farming. (Surely at some point there's been a sport that involves cannon, tho...)
There was also a tradition at our high school to shoot off a cannon each time our football team scored a point at home games (just the powder no projectile).