There is enough logging in iOS to show when your extension loads and unloads. Your extension can't be too large or it will not load - and that is logged too.

Xcode 12.0.1 has a Persistent Token Extension template. Note that extensions are limited in size. The exact size varies but is 5-6Mb Be careful about the frameworks and libraries in your extension. If your extension is too big, an error will be logged.

On MacOS, my extension is loaded and I am asked to make a TKSmartCardTokenDriver but the TKSmartCardSlot is created for me. Do I need to create a TKSmartCardSlot object? If so, I don't see a way to do that.

Got this working. Just had incorrect bundle IDs.

Related to this topic, our Sub Rosa product performs certificate based TLS authentication using a smart card. We use UIWebView and an NSURLProtocol subclass to implement our own HTTPS and TLS layers. Our use case is this: we need to be able to deliver a certificate to WKWebView AND be able to provide the crypt result for the TLS Certificate Verify signature. If we could implement a SecKey where our code handles the signature for TLS that would be a solution. I don't believe CryptoTokenKit is available on iOS even though the documentation says it is. If we could use WKURLSchemeHandler that would be a solution, but WKURLSchemeHandler does not support redirection, and our app would need to re-write URL schemes and that may lead to security problems. If we could create/extend a URLCredential that would contain the certificates and TLS signature similar to init(identity: SecIdentity, certificates: [Any]?, persistence: URLCredential.Persistence) that would be a solution (and one that we would prefer).

The feedback assistant number for my issue is FB7760918 There is no adequate replacement for UIWebView and NSURLProtocol for custom TLS certificate authentication.