nix copy never finishes when used from MacOS host and copying to remote servers with ssh or ssh-ng

[onnimonni]

Describe the bug

Whenever I'm trying to use nixos-anywhere it just hangs when trying to copy disko module to remote server. I have narrowed this issue down to nix copy. See more here nix-community/nixos-anywhere#385.

I have installed my nix with the nix determinate systems installer.

$ sw_vers
ProductName:		macOS
ProductVersion:		14.6.1
BuildVersion:		23G93
$ ssh -V
OpenSSH_9.9p1, OpenSSL 3.3.2 3 Sep 2024

Steps To Reproduce

1. Install UTM
   2: Try to initialize the VM with the following steps:

# Create new nix configuration for UTM vm
$ nix flake new -t github:ciderale/nixos-utm my-utm-vm

$ cd my-utm-vm
# Replace the ssh key with the key that comes first from your ssh-agent
$ sed -i'' -e "/ssh-ed25519/ s/.*/    \"$(ssh-add -L | head -n1)\"/" configuration.nix
# Initialize the UTM vm
$ nix run github:ciderale/nixos-utm#nixosCreate .#utm

This then hangs when installing disko script (last output is ### Building disko script ###) and I have narrowed it down to this command:

nix copy --extra-experimental-features 'nix-command flakes' --no-write-lock-file -L --substitute-on-destination --to ssh://[email protected] '.#nixosConfigurations."utm".config.system.build.diskoScript' --derivation --no-check-sigs --debug  --print-build-logs --verbose &> stdout-log.txt

I tried to replace ssh-ng to ssh and it hangs similiarly for both. When I'm running this command from a linux host everything works properly.

Expected behavior

Installer should finish and not hang into the step where it copies disko modules to the remote server. This happens both with UTM local virtual machine and remote servers for me.

nix-env --version output
nix (Nix) 2.24.5

Additional context

Here are the logs from my attempt to use the above nix copy command:
stdout-log.txt

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