Misterio77/nix-config
Gabriel Fontes
A widely copied personal config, with a clean separation of hosts, users and shared modules.
Worth borrowing: How it splits system settings from per-user Home Manager settings.
Second round
ryan4yin/nix-config
Ryan Yin
From the author of the NixOS & Flakes Book: desktops, servers and macOS, all in one place.
Worth borrowing: Read it next to the book: the chapters map onto real code here.