I keep seeing people refer to a “front page” which isn’t really a thing that exists since it’s completely different depending on which instance you’re on, which feed you’re looking at and how you sort it, but I have no idea what that was on Reddit either since I always stuck to my subscriptions.

"front page" is just your "subscribed" feed here.

The other difference here is that we don't have an "/r/all" (meaning everything on reddit), there is the "local" feed, that would be, "all" communities of the specific instance.

And there is an "All" feed, but it isn't all the communities on every instance, there you only see all the communities any user of your instance is subscribed to.