I have a simple webapi solution (aspnet core 2.1) consisting of two projects, Test.api (containing a controller) and Test.Models. The Models project has Newtosoft package and uses JsonIgnore attribute on models. When I deploy this solution to Azure app service and view the contents of the deployed folder via cloud explorer (also used kudu), I don't see the Newtosoft dll.
Where is it being referenced from? Does app service have an equivalent of GAC?
I don't know how the GAC works for .NET Core but it should reflect a regular Windows system, in essence that's what App Service with Windows workers is, Windows Server + special sandbox.
Just dir /a /s newtonsoft*.dll from root of D drive in Kudu and it should point you to the DLL in GAC.