This gives us Nix 2.32 for use in CI's Eval job and nixfmt 1.1.0.
From the nixpkgs-unstable channel:
https://hydra.nixos.org/build/311062898#tabs-buildinputs
Changes for treefmt-nix:
5eda4ee812...f56b1934f5
Co-authored-by: Wolfgang Walther <walther@technowledgy.de>