If you are using an Apple Silicon laptop and you want to deploy to an x86-64 Linux box, this can get a bit annoying due needing to deal with cross compilation in nix.
server:
@echo "Deploying machine (with ssh-agent forwarding): '$(MACHINE)'"
NIX_SSHOPTS="-A" \
nix run nixpkgs#nixos-rebuild -- switch \
--flake .#$(MACHINE) \
--target-host $(MACHINE).$(DOMAIN) \
--build-host $(MACHINE).$(DOMAIN) \
--no-reexec \
--verbose \
--sudo
This uses ssh agent forwarding, and then sudo via PAM. That allows for passwordless sudo. Building (well, activating) without sudo is pretty involved last I checked, I could not get it to work.