Communism most certainly doesn’t require centralized planning - all it requires is a method of providing start up capital without giving away ownership.

It could be from local government taxes, federal coining of money, crowdsourced or some combination of these - you’d just need a mechanism of some sort to give loans to groups looking to start a worker-owned company. That’s the only requirement

There’s an infinite number of ways to slice it - centralized planning is super worrisome IMO because it creates a locus of power. But not only is it unnecessary, the same result can be achieved far more effectively with a digital marketplace that matches buyers and sellers. You just have to remove incentives and power from the entities managing it - with a fairly small amount of money, you could host a standard system with an open and auditable code base

But you could also just design an open market without ownership of companies - that’s communism. You’d have to decommodify certain basic needs and shape incentives carefully, so it’s a bit more complicated than that… But not much