Try this: https://lemmyverse.net/communities

Part of the issue is that, despite some explosive growth in the last month, Lemmy / Kbin are still fairly small (especially when compared to Reddit). If you came here from Reddit expecting the same breadth, you’ll be disappointed, unfortunately. However, that’s not a forever problem. Rather than looking for subs for very specific interests (e.g. a specific make of car), try joining subs for cars in general, where you’ll find more active discussion, and posting topics related to your make there. Alternately, try creating the specific subs - but keep in mind that the user numbers just might not support it (yet). We’ll get there.

I don’t know much about lemmy.fmhy.ml - but if it’s a newer or smaller instance, it could be that it hasn’t yet learned about all of the other instances / communities out there - you can solve that problem, too, if you find the communities you’re interested in at the link above, and search them out and interact with them on your instance. This will make that content start showing up in your instance’s All feed (for all users).