In multiplatform mobile projects the network stack is typically based on Ktor Client with Darwin Engine https://ktor.io/docs/client-engines.html#darwin
When using this engine the network instrumentation is not applied.
This is probably related to method swizzling applied to methods that are not effectively the ones used by the Darwin Engine.
Source code is here https://github.com/ktorio/ktor/tree/main/ktor-client/ktor-client-darwin/darwin/src/io/ktor/client/engine/darwin
Note: other SDKs seem to use NSURLSessionConfiguration for hooking into network calls. Would it be a feasible alternative approach to method swizzling?