It is quiet here! At least at first. Lemmy does not have millions of users, more like hundreds of thousands. Also, there tends to be a lot of content shared that gets zero comments. This doesn't mean no one cares, it's just that a lot of the content is of the nature "hey, here's a good article about black holes or sea sponges or whatever" and that's it. No need for a discussion, just sharing interesting stuff. (There are definitely discussions like on reddit though depending on topic/community)

https://youtu.be/K8fBSrhHrE8

This is a decent video that shows some of the basics.

Also, you probably have your default setting showing you your "home" feed when you start the app. This only shows you communities/users you have followed (called subscribed here). The "all" feed shows you everything, and "local" shows you everything on your server. Start with "all" until you have figured out at least some aubscriptions.