Hi @JimJ92120 !
Thanks for your answer! 
May I ask where did you put your config in a freshly installed NixOS system (not yet rebooted)? Did you generate a new config through nixos-generate-config and applied it there?
Because once NixOS is installed through Calamares, where do I find the future system’s configuration? Because I presume I’ll have to apply it there (and then nixos-rebuild switch), right?
Thanks for your help