Since .NET 5, using `InternalsVisibleTo` MSBuild items is [supported out of the box](https://github.com/dotnet/sdk/blob/v5.0.102/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.GenerateAssemblyInfo.targets#L108-L112) thanks to https://github.com/dotnet/sdk/pull/3439. I think it would be worth mentioning it in the README in order to avoid potential confusion.