to reproduce, simply enable neovim and have a flake with something similar to these inputs:

  inputs = {
    # points to 634fd46 at the time of writing this
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";

    catppuccin = {
      url = "github:catppuccin/nix";
      inputs = {
        nixpkgs.follows = "nixpkgs";
        # disable inputs we don't need
        nixpkgs-stable.follows = "";
        home-manager.follows = "";
        home-manager-stable.follows = "";
        nuscht-search.follows = "";
        catppuccin-v1_1.follows = "";
        catppuccin-v1_2.follows = "";
      };
    };

i'm afraid i currently don't have the resources to do a full nixpkgs bisect since i can't build every derivation due to computing constraints, but c207a2b should be a bad commit while d3c42f1 (currently in the lockfile) is good, to narrow things down at least a bit.

here is the full log output, but the following lines are probably sufficient:

All lua modules were checked.

Require check failed for the following modules:
  - catppuccin.groups.integrations.feline
  - catppuccin.groups.integrations.noice
  - catppuccin.lib.vim.init

nixpkgs seems to just disble these modules, as can be seen here; i'll open a pr adding the override's changes as from my testing.

however, all of this feels rather weird (i have no clue why the plugin suddenly breaks), i barely know what any of this stuff does and there might be better solutions.