I have tried to install dotnet core, but it does not worked. So, I would like to uninstall it and start refresh. How can I uninstall dotnet core from macOS Sierra(10.12.3).
You might as well use dotnet-core-uninstall tool which allow you to select a specific SDK or runtime version to remove. github docs
If you are experiencing issues with building Xamarin.Mac after installing preview version of .Net 5 SDK you might like to remove Mono using such script and Visual Studio like this and try to reinstall from scratch
good luck