The default ASP.NET Core server is Kestrel which runs in-process and is cross platform. Kestrel has officially supported gRPC for over a year now[1]. That linked GitHub comment is specifically about IIS gRPC support which relies on HTTP.sys (which runs in kernel mode and is tied to the Windows shipping cycle as noted).

[1]: https://docs.microsoft.com/en-us/aspnet/core/grpc/?view=aspn...