I need to create a COM class in .NET8 that needs to be accessible to Excel.

After watching this video, I implemented the following test bed class:

namespace COMTestBedCS
{
    [Guid("26a0aa6d-5aba-458f-92b4-b9a30ae0c65c")]
    [GeneratedComInterface]
    public partial interface ITestBed
    {
        int GetXPTO();
        void SetXPTO(int value);
    }

    [Guid("3e178f98-522e-4e95-8a9c-6d80dc48b7d5")]
    [GeneratedComClass]
    public partial class TestBed : ITestBed
    {
        private int _XPTO = 1024;

        public int GetXPTO() => _XPTO;
        public void SetXPTO(int value)=>_XPTO = value;
    }
}

The project compiles correctly, without errors. However, when I try to reference this test bed in Excel, I get the following error: Can't add a reference to the specified file.

If I try to use regsvr32, I get the following error:

What am I doing wrong?

For completion sake, here’s the project file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
  </PropertyGroup>

</Project>