If anyone finds this helpful, this is how I've turned that into a flake.nix:

{
  description = "Basic .NET 7 flake";

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem
      (system:
        let pkgs = nixpkgs.legacyPackages.${system}; in
        {
          devShells.default = 
            pkgs.mkShell {
              buildInputs = with pkgs.dotnetCorePackages; [ sdk_7_0 ];

              DOTNET_ROOT = with pkgs; "${dotnet-sdk_7}";
            };
        }
      );
}

hi, i had a go at packaging a dotnet project
i've got something, but the binary does nothing but return 255

https://github.com/NixOS/nixpkgs/commit/7d7d2bfee091dd389eb51bdac1a363cfc27643b4

I don't see anything obvious in your code, but I'm getting a weird error when building all dotnet packages for some reason

error: builder for '/nix/store/rscfr5ivym33v9w1n7p20zbarn5cif77-tjaplayer3-f-1.8.2.1-dependencies-source.drv' failed with exit code 139;
       last 1 log lines:
       > /nix/store/a4v3az5zmqfc2x3gyjgds5azgdhf9b54-stdenv-linux/setup: line 1560:     7 Segmentation fault      (core dumped) nuget init "/nix/store/gv7vh34zghgnmla0qjgfgzxmvjxb6k2d-tjaplayer3-f-1.8.2.1-nuget-deps" "$out/lib"```
An error that I'm getting for a different derivation, getting the same for all my dotnet derivations

I don't see anything obvious in your code, but I'm getting a weird error when building all dotnet packages for some reason

error: builder for '/nix/store/rscfr5ivym33v9w1n7p20zbarn5cif77-tjaplayer3-f-1.8.2.1-dependencies-source.drv' failed with exit code 139;
       last 1 log lines:
       > /nix/store/a4v3az5zmqfc2x3gyjgds5azgdhf9b54-stdenv-linux/setup: line 1560:     7 Segmentation fault      (core dumped) nuget init "/nix/store/gv7vh34zghgnmla0qjgfgzxmvjxb6k2d-tjaplayer3-f-1.8.2.1-nuget-deps" "$out/lib"
```
An error that I'm getting for a different derivation, getting the same for all my dotnet derivations

I don't see anything obvious in your code, but I'm getting a weird error when building all dotnet packages for some reason

error: builder for '/nix/store/rscfr5ivym33v9w1n7p20zbarn5cif77-tjaplayer3-f-1.8.2.1-dependencies-source.drv' failed with exit code 139;
       last 1 log lines:
       > /nix/store/a4v3az5zmqfc2x3gyjgds5azgdhf9b54-stdenv-linux/setup: line 1560:     7 Segmentation fault      (core dumped) nuget init "/nix/store/gv7vh34zghgnmla0qjgfgzxmvjxb6k2d-tjaplayer3-f-1.8.2.1-nuget-deps" "$out/lib"

An error that I'm getting for a different derivation, getting the same for all my dotnet derivations

I don't see anything obvious in your code, but I'm getting a weird error when building all dotnet packages for some reason

error: builder for '/nix/store/rscfr5ivym33v9w1n7p20zbarn5cif77-tjaplayer3-f-1.8.2.1-dependencies-source.drv' failed with exit code 139;
       last 1 log lines:
       > /nix/store/a4v3az5zmqfc2x3gyjgds5azgdhf9b54-stdenv-linux/setup: line 1560:     7 Segmentation fault      (core dumped) nuget init "/nix/store/gv7vh34zghgnmla0qjgfgzxmvjxb6k2d-tjaplayer3-f-1.8.2.1-nuget-deps" "$out/lib"

An error that I'm getting for a different derivation, getting the same for all my dotnet derivations

In reply to @raphi:tapesoftware.net
ugh mkNugetSource is using mono to run nuget

In reply to @raphi:tapesoftware.net
yeah i was looking into it. the closest thing the .net core CLI has is dotnet nuget push which doesn't have the same semantics