More active than hive: https://www.reddit.com/r/raspberry_pi/. But you are right, it's definitely a niche thing.
Its hard enough for me to have good content to post in programming, even harder to find others who'll post in there. I'll give you a post in there sometime next week if my computer doesn't burn up and die.
How about Hive Gaming? It seems active here and a lot of people love games.