wasmtime cannot be installed in an VSTO office addin

Hi,
I would like to use wasmtime in an VSTO C# office addin project.
However, I have trouble installing wasmtime as the prerequisites do not match.
wasmtime requires .NetStandard 2.1.
But the addin uses .Net framework 4.7.2. and according to https://docs.microsoft.com/en-us/dotnet/standard/net-standard .NetStandard 2.1 is not supported by .Net framework.

Also https://devblogs.microsoft.com/dotnet/announcing-net-standard-2-1/ states
> Given many of the API additions in .NET Standard 2.1 require runtime changes in order to be meaningful, .NET Framework 4.8 will remain on .NET Standard 2.0 rather than implement .NET Standard 2.1

The following workaround also did not work: https://stackoverflow.com/questions/42039069/could-not-install-package-you-are-trying-to-install-this-package-into-a-pr

Also, trying to use net5.0 ("net5.0") breaks the addin.

Anyone has some advice?