This is quite an interesting ‘meta’ question. Because my system is clearly influenced, in scheme and name, by Dewey Decimal. It’s just a flavour of it, really.
I feel like on one side you’ve got rigid hierarchy. That’s JD, or flavours of it. And on the other side — and I don’t use it, so I might be wrong — you’ve got Obsidian links all over the shop. Massively connected, and as a necessity therefore not rigidly hierarchical.
Your brain works one of these ways, and you choose the system that suits you. And there’s all sort of systems in the middle, like PARA feels like it’s in the middle? (I confess to only knowing it by association.)
So to your question, are there other methods? If we say that JD is an implementation of the method which is a rigid structure, then I don’t know that there are. I think we’d have discovered them by now.
Related, a colleague sent me this video. The way this guy lays out the matrix is kinda what I’m trying to say here. Methods are positions on the matrix, in my view.