Though mostly undocumented, setting nix.settings.substituters overwrites any previous entries, including the default nixpkgs binary cache. Using nix.settings.extra-substituters appends to the list instead, independent of any nixpkgs or NixOS module logic.
See the nix manual entry
Though mostly undocumented, setting
nix.settings.substitutersoverwrites any previous entries, including the default nixpkgs binary cache. Usingnix.settings.extra-substitutersappends to the list instead, independent of any nixpkgs or NixOS module logic. See the nix manual entry