As I see it, you have three options:
- Revert back to an earlier RhinoCommon nuget package
- Add new build flavors (Debug-Rhino7, Release-Rhino7) to your shared project that references Newtonsoft.Json.Rhino instead of Newtonsoft.Json
- Use extern alias to reference Newtonsoft.Json in your plug-in code (extern alias - C# Reference | Microsoft Docs)
I would recommend option (2). This lets you ship without a copy of Newtonsoft.Json for Rhino 7. We built a vendorized version of the DLL as we were getting version mismatch conflicts due to the fact that so many people use Newtonsoft.Json and there are so many versions out there. For option (2) it usually required some manual editing of the csproj file, but we can help here if you choose to go that route.