For a full .NET project you can tick a box to make the project COM Visible in Project Properties > Application tab > Assembly Information..:
However, the Assembly Information.. button doesn't exist for .NET Standard projects, instead that data is entered on the Project Properties > Package tab, but that tab doesn't have a checkbox for Make Assembly COM-Visible:
Can you still make .NET Standard libraries COM Visible by some other method, or does it not make sense to do that for some reason?