Did you search the posts here? See NixOS automatic unattended offline installer USB stick, More airgap questions - #13 by kotatsuyaki, Using NixOS in an isolated environment - #23 by ejpcmac, etc.
Did you search the posts here? See NixOS automatic unattended offline installer USB stick, More airgap questions - #13 by kotatsuyaki, Using NixOS in an isolated environment - #23 by ejpcmac, etc.