I’m running a standalone Lemmy instance, but I’m not planning to develop or grow a community on said instance since it’s mostly to practice my infra and DevOps skills. I would, however, like to subscribe to all communities on other instances, for example, on lemmy.world and several others. Is there an easy way, or can I only subscribe to each community individually?
If you want to see all of them, you can change the setting from “subscribed” to “all”
The point you’re missing is that Lemmy only federates posts from communities with at least one subscriber from the home instance.
So if you have a single-user personal instance, you won’t see any posts on All except ones from communities you personally subscribe to.
I’m not aware of any method to mass-fetch federations, to answer OP.