It would be great if we also can manage to switch from C to C.utf-8 locales in stdenv and our glibc package as many applications now expect unicode locales (i.e. python). Debian and Fedora are already on board with this. Also since systemd has now support for that too
UPDATE Tracking issue: glibc: C.UTF-8 locales by Mic92 · Pull Request #54485 · NixOS/nixpkgs · GitHub