The instances of the fediverse are necessarily smaller than the reddit server, therefore you will have to search for remote communities on specialized servers. Or start your own.
If meditation concerns 0.1% of the population, then you will need 10000 accounts for each 10 meditation members, that would be 40 people on kbin. So you have to search on different instances, and maybe move to a different federation. Your main instance should be located where you live and then you search elsewhere for your niche interests.