Recreational mapmaking.
Every couple of months the family and I will book out some long weekend to just go to an Airbnb in some random town with some copy paper and just go around trying to draw what we think is around us. Inevitably the lines collide and we have to ask some local passerby for help, and if they know any interesting places nearby, and before you know it they're following along with a colored pencil and some copy paper against a hardcover book too.
Now that's a niche hobby that sounds interesting.