The response to nix registry list is the following
user flake:nixpkgs-unstable github:NixOS/nixpkgs/nixpkgs-unstable
system flake:nixpkgs path:/nix/store/ib2yidi0ql2j9vp3khg5lpv4ayncgs9p-zml54rvr3wy3j177765pii32852zrv4p-source?narHash=sha256-O1XDr7EWbRp%2BkHrNNgLWgIrB0/US5wvw9K6RERWAj6I%3D%0A
global flake:agda github:agda/agda
global flake:agenix github:ryantm/agenix
global flake:arion github:hercules-ci/arion
global flake:blender-bin github:edolstra/nix-warez?dir=blender
global flake:bundlers github:NixOS/bundlers
global flake:cachix github:cachix/cachix
global flake:composable github:ComposableFi/composable
global flake:disko github:nix-community/disko
global flake:dreampkgs github:nix-community/dreampkgs
global flake:dwarffs github:edolstra/dwarffs
global flake:emacs-overlay github:nix-community/emacs-overlay
global flake:fenix github:nix-community/fenix
global flake:flake-parts github:hercules-ci/flake-parts
global flake:flake-utils github:numtide/flake-utils
global flake:helix github:helix-editor/helix
global flake:hercules-ci-agent github:hercules-ci/hercules-ci-agent
global flake:hercules-ci-effects github:hercules-ci/hercules-ci-effects
global flake:home-manager github:nix-community/home-manager
global flake:hydra github:NixOS/hydra
global flake:mach-nix github:DavHau/mach-nix
global flake:ngipkgs github:ngi-nix/ngipkgs
global flake:nickel github:tweag/nickel
global flake:nix github:NixOS/nix
global flake:nix-darwin github:nix-darwin/nix-darwin
global flake:nix-serve github:edolstra/nix-serve
global flake:nixops github:NixOS/nixops
global flake:nixos-anywhere github:nix-community/nixos-anywhere
global flake:nixos-hardware github:NixOS/nixos-hardware
global flake:nixos-homepage github:NixOS/nixos-homepage
global flake:nixos-search github:NixOS/nixos-search
global flake:nixpkgs github:NixOS/nixpkgs/nixpkgs-unstable
global flake:nixvim github:nix-community/nixvim
global flake:nur github:nix-community/NUR
global flake:patchelf github:NixOS/patchelf
global flake:poetry2nix github:nix-community/poetry2nix
global flake:pridefetch github:SpyHoodle/pridefetch
global flake:sops-nix github:Mic92/sops-nix
global flake:systems github:nix-systems/default
global flake:templates github:NixOS/templates
I see the error. I was using the wrong branch as nixpkgs-unstable input. It should have been nixos-unstable all along