`nix profile install` fails: libgit2 error 9 – missing blob in `SimulaVR/environments@91bb377`

I was testing whether Simula works as a potential display server/compositor for Rokid Max 1st gen AR glasses (considering a purchase). Installation via the documented Nix flake command fails during evaluation.

Environment

• OS: CachyOS (Arch-based) x86_64
• Nix: Flakes-enabled, non-NixOS
• Hardware: ThinkPad E14 Gen 5, AMD Radeon graphics
• Command run from: clean shell, no local clone

Command

nix profile install github:SimulaVR/Simula

Error Output

~
❯ nix profile install github:SimulaVR/Simula
warning: 'install' is a deprecated alias for 'add'
warning: ignoring untrusted substituter 'https://simula.cachix.org', you are not a trusted user.
Run `man nix.conf` for more information on the `substituters` configuration option.
warning: ignoring the client-specified setting 'trusted-public-keys', because it is a restricted setting and you are not a trusted user
error:
       … while calling the 'derivationStrict' builtin
         at «nix-internal»/derivation-internal.nix:37:12:
           36|
           37|   strict = derivationStrict drvAttrs;
             |            ^
           38|

       … while evaluating derivation 'simula-0.0.0'
         whose name attribute is located at «github:nixos/nixpkgs/23d72dabcb3b12469f57b37170fcbc1789bd7457?narHash=sha256-z5NJPSBwsLf/OfD8WTmh79tlSU8XgIbwmk6qB1/TFzY%3D»/pkgs/stdenv/generic/make-derivation.nix:541:13

       … while evaluating attribute 'installPhase' of derivation 'simula-0.0.0'
         at «github:SimulaVR/Simula/2fbec171759f5e0d7cca2d121dfd081d476c0073»/flake.nix:421:15:
          420|
          421|               installPhase = ''
             |               ^
          422|                 runHook preInstall

       (stack trace truncated; use '--show-trace' to show the full, detailed trace)

       error: looking up file '«git+https://github.com/SimulaVR/environments?ref=refs/heads/master&rev=91bb3777d558e809be12bcc94f6c984487994765&shallow=1»/AllSkyFree_Sky_AnotherPlanet_Equirect.png': object not found - no match for id (6f37903fa7bf58d67d2bee12454315a577f56903) (libgit2 error code = 9)

~
❯ 

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Observed Behavior

Nix evaluation fails when attempting to fetch a file from the environments input at the pinned revision 91bb3777d558e809be12bcc94f6c984487994765. The error references a specific blob ID (6f37903fa7bf58d67d2bee12454315a577f56903) that the Git fetcher cannot resolve.

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Expected Behavior

nix profile install github:SimulaVR/Simula should successfully evaluate the flake, fetch all inputs (including environments), and build/install the simula package.

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Steps to Reproduce

1. Run nix profile install github:SimulaVR/Simula on a flakes-enabled Nix installation (non-NixOS)
2. Observe evaluation failure during installPhase

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Additional Context

• The environments input is used to copy skybox assets into the Nix store during installPhase.
• I have not cloned the repository locally; this occurs with a direct flake reference.

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Request

Could maintainers verify whether the environments repository at revision 91bb3777d558e809be12bcc94f6c984487994765 contains the referenced blob for AllSkyFree_Sky_AnotherPlanet_Equirect.png? If the object is missing, updating the pinned revision or providing a local-build workaround in the README would help unblock installation attempts.

Note: I am filing this as a user evaluating Simula for potential use with AR glasses; I do not have push access to either repository. Happy to provide additional logs if helpful.

Inspect flake.nix around the installPhase at line 421 and trace how the environments input is pinned and used for AllSkyFree_Sky_AnotherPlanet_Equirect.png. Verify whether revision 91bb3777d558e809be12bcc94f6c984487994765 contains the referenced blob, then test the documented nix profile install command. Done means the flake evaluates and the simula package can be installed, or the README documents a confirmed workaround.