If someone is interested, I'm the amin of an instance focused on functional programming: https://functional.cafe
Jokes apart, I'm trying my best to make it a more technical instance, but I can't control what the users toot. I just hope that someone joins a tech instance to talk about tech...
I think the point of an instance with a topic has more to do with the fact that people on that instance tend to be people with similar interests to you, not that every single post is about that topic.