Nixpkgs please! It's the most successful reproducibility experiment I know of.
Fun fact: all of the current website's infra is NixOS-based
Fun fact #2: I overhauled Bitcoin Core's reproducible build system to use Guix (a Nix-inspired functional package manager)
All the nix deployment tools had too much magic and broke, but nixos-rebuild always works and it's part of Nix!
Disko was great for bootstrapping servers: https://github.com/nix-community/disko
Fun fact: all of the current website's infra is NixOS-based
Fun fact #2: I overhauled Bitcoin Core's reproducible build system to use Guix (a Nix-inspired functional package manager)