nixos
I use flakes for managing my homeserver that’s running NixOS. The non-flake version of Nix uses channels, and any nix shell created on a system that doesn’t use flakes also seems to inherit package versions from whatever channel the system is using. For my flake-based setup, I’m using the unstable channel to import nixpkgs. However, the nix shell appears to use some really old (stable?) channel of nixpkgs, giving me really old package versions if I need to spin up an ad-hoc shell for something.