literally just click "all"
That said, sometimes it takes forever to load content from other servers, and there isn't any caching that I can see. When I go back from a post it all struggles to reload again.
^ This. It seems to take several minutes then you get a massive flood from multiple servers. Also change how it is sorted will give you different results.
It seems to be broken right now, but https://lemmy.directory/ attempts to be this. The "all" posts feed on your instance shows all posts In communities that someone on your instance subscribes to (which might be quite a lot of communities on a big instance, or the same as your own subscribed list on a single-user instance).
lemmy.directoryhas some script that tries to automate subscribing to everything, so it can be a true /r/all analog.I'm using the jerboa app. Just need to change Local to All in the top left. Sometimes it changes back. I also need to be very particular in how it sorts or it's the same top posts for days.
Also in Jerboa. Go top left, settings, "user name" settings. And then you can change to All / New or All / Top day as the default on startup
