{
  "sdk": {
    "version": "6.0.100-preview.4.21262.10",
    "allowPrerelease": false,
    "rollForward": "latestMajor"
  }
}

{
  "sdk": {
    "version": "6.0.100-preview.4.21255.9",
    "allowPrerelease": false,
    "rollForward": "latestMajor"
  }
}

Use correct .NET 6 preview 4 SDK
Use correct .NET 6 preview 4 SDK

Use the official build of the .NET 6 preview 4 SDK.