I'm setting up a new ARTIQ system and follow the manual (installing via nix (version 2.12.0), on Ubuntu 22.04). When trying to spawn the shell via nix shell I get the following error:
error: input 'extrapkg/daxpkgs/nixpkgs' follows a non-existent input 'extrapkg/artiq/nixpkgs'
How can I resolve this error? (sorry if that is an error on my side, but I'm not very familiar with nix)

I think there is some work going on at the dax packages/artiq packages nix files.
@sb10q @bradb

Ah yeah sorry about that, there's been a change to artiq-extrapkg. Try adding the following lines to your flake:

  inputs.daxpkgs = {
    url = git+https://gitlab.com/duke-artiq/dax.git;
    inputs = {
      artiqpkgs.follows = "artiq";
      nixpkgs.follows = "artiq/nixpkgs";
      sipyco.follows = "artiq/sipyco";
    };
  };
  inputs.extrapkg.inputs.daxpkgs.follows = "daxpkgs";

You'll also need to add daxpkgs to the output arguments:

  outputs = { self, artiq, extrapkg, daxpkgs }:

Sorry about the verbosity -- less verbose approaches aren't working for me

    @bradb That's excessively verbose and I think there should be a shorter solution.

    bradb And please do not nominate breaking changes like this for release-7.