I had the same question a while ago, which never got resolved. I am building a plugin using Rhino7 Mac and Visual Studio Mac, and when I reference a DLL, I got this warning.
I understand this has something to do with RhinoCommon version compatibility, but I have updated both Rhino and the Rhino NuGet package in visual studio. Strangely enough, I still see their versions differ as in the attached screen capture. Sometimes the warning goes away when hitting the “Run Script” button in the editor multiple times.
You need to add an ‘app.config’ file to the DLL’s project - right-click it in visual studio, select “Add new item”, then search for the application config: