https://nixos.org/download.html (when in doubt, try single user install)
(only applicable if this is still experimental like at time of writing) https://nixos.wiki/wiki/Flakes#Permanent
nix build --no-link .#homeConfigurations.pepper.activationPackage
"$(nix path-info .#homeConfigurations.pepper.activationPackage)"/activatehome-manager switch --flake ".#pepper"