I had to do this on Reddit over the years. I have zero interest in sport, for example. And it seems there are thousands of individual communities for every sport, every team, all over the world.
I truly don’t care about them, and would like to just block - maybe via a community containing certain words? “Football” for example?
The app I’ve been using (connect) has a manual filter via keywords, which might be along the lines of what you’re looking for. I’m not sure if there’s anything native that does it (yet) though.