I encountered the same problem as
and can get it to work by changing skd to sdk.web
I have a test project where I create a AppSelfHostBased for integration test and since moving from netcore3.1 to net5 I get in the OneTimeSetUp
System.TypeLoadException : Could not load type ‘Microsoft.Extensions.Primitives.InplaceStringBuilder’ from assembly ‘Microsoft.Extensions.Primitives, Version=126.96.36.199, Culture=neutral, PublicKeyToken=adb9793829ddae60’.
The template project for ServiceStack works so is there no other solution to change sdk to sdk.web?