Were you able to figure this out? I'm in the same boat right now.

I still haven't resolved this issue. My problem is that our main app has an enterprise configuration. Even when I have the Xcode scheme configured not to build the enterprise configuration, it still validates the certificates for both the release and enterprise configuration of the parent app. Is there any way to prevent it from trying to embed and validate the app clip for an enterprise configuration? The only way I've been able to get around it so far is to manually set all the configurations in the parent app to use the app store release bundle ID and certificate when I need to build and embed the app clip.

I was able to solve this by trusting the app developer in settings. It's a very un-obvious step that isn't alluded to in the error Xcode Previews gives you. On your device you're trying to preview on... Open Settings Navigate to General > VPN & Device Management You should see the app you're trying to preview listed in here. If you don't see it, try to build and run the app to the physical device first and then repeat these steps. Select the app and then "Trust" the developer