Please install Nix with Nix Flakes with nix-installer.

curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install

For the first time, since home-manager is not installed, build via the nix run command:

nix run home-manager/master -- switch --flake .#koralle

From the second time onwards, since home-manager is installed, the command becomes slightly simplified:

home-manager switch --flake .#koralle

I have further simplified this using just and justfile.

just switch

or

just s