Ruri: managed to make it compile with the following code:

{
  lib,
  fetchFromGitHub,
  buildDotnetModule,
  dotnetCorePackages,
  mono,
  dotnet-sdk,
  openssh,
}:

buildDotnetModule rec {
  fullSrc =
    (fetchFromGitHub {
      owner = "Assistant";
      repo = pname;
      rev = "66649a2a343797a98f3228172ffc17052f5442d1";
      sha256 = "sha256-iG49/XLi3Skhp8NY5IAqSU5IfMj4y4GNIm2huewiu9Q=";
      fetchSubmodules = true;
    })
    .overrideAttrs (_: {
      GIT_CONFIG_COUNT = 1;
      GIT_CONFIG_KEY_0 = "url.https://github.com/.insteadOf";
      GIT_CONFIG_VALUE_0 = "git@github.com:";
    });

  pname = "Hive";
  version = "0.0.1";
  src = fullSrc;

  projectFile = "src/Hive/Hive.csproj";
  nugetDeps = ./deps.nix;

  dotnet-sdk = dotnetCorePackages.sdk_6_0;
  dotnet-runtime = dotnetCorePackages.aspnetcore_6_0;

  dotnetInstallFlags = [ "--framework" "net6.0" ];
  #testProjectFile = "src/Hive.Test/Hive.Tests.csproj";

  meta = with lib; {
    homepage = "https://github.com/Atlas-Rhythm/Hive";
    description = "A general backend project for modding communities";
    license = licenses.agpl3Only;
  };
}

In reply to @magikarpz:matrix.org

Ruri: managed to make it compile with the following code:

{
  lib,
  fetchFromGitHub,
  buildDotnetModule,
  dotnetCorePackages,
  mono,
  dotnet-sdk,
  openssh,
}:

buildDotnetModule rec {
  fullSrc =
    (fetchFromGitHub {
      owner = "Assistant";
      repo = pname;
      rev = "66649a2a343797a98f3228172ffc17052f5442d1";
      sha256 = "sha256-iG49/XLi3Skhp8NY5IAqSU5IfMj4y4GNIm2huewiu9Q=";
      fetchSubmodules = true;
    })
    .overrideAttrs (_: {
      GIT_CONFIG_COUNT = 1;
      GIT_CONFIG_KEY_0 = "url.https://github.com/.insteadOf";
      GIT_CONFIG_VALUE_0 = "git@github.com:";
    });

  pname = "Hive";
  version = "0.0.1";
  src = fullSrc;

  projectFile = "src/Hive/Hive.csproj";
  nugetDeps = ./deps.nix;

  dotnet-sdk = dotnetCorePackages.sdk_6_0;
  dotnet-runtime = dotnetCorePackages.aspnetcore_6_0;

  dotnetInstallFlags = [ "--framework" "net6.0" ];
  #testProjectFile = "src/Hive.Test/Hive.Tests.csproj";

  meta = with lib; {
    homepage = "https://github.com/Atlas-Rhythm/Hive";
    description = "A general backend project for modding communities";
    license = licenses.agpl3Only;
  };
}

{ pkgs ? import <nixpkgs> {} }:

pkgs.symlinkJoin {
  name = "dotnet-pack";
  paths = [ pkgs.dotnet-sdk_8 pkgs.dotnet-sdk_7 pkgs.dotnet-sdk ];
  postBuild = ''
    rm -rfv $out/bin
    rm -rfv $out/dotnet
    cp -rv ${pkgs.dotnet-sdk_8}/dotnet $out/
    cp -rv ${pkgs.dotnet-sdk_8}/bin $out/
  '';
}

wanted to share this derivation incase anyone ever needed to use multiple dotnet versions at once

[Rory@Rory-desktop:/Rory-Open-Architecture]$ dotnet --list-sdks
6.0.414 [/nix/store/g0j4gcarcbqkxl3i14h4ls3qsmyjdc2m-dotnet-pack/sdk]
7.0.401 [/nix/store/g0j4gcarcbqkxl3i14h4ls3qsmyjdc2m-dotnet-pack/sdk]
8.0.100-rc.1.23455.8 [/nix/store/g0j4gcarcbqkxl3i14h4ls3qsmyjdc2m-dotnet-pack/sdk]