DriverKit driver doesn't appear in Settings when installed with iPad app

Question

I'm working on a DriverKit driver. I have it running on macOS, including a very simple client app written in SwiftUI. Everything is working fine there. I've added iPadOS as a destination for the app as demonstrated in the WWDC video on DriverKit for iPadOS. The app builds and runs on my iPad, as expected (after a little work to conditionalize out my use of SystemExtensions.framework for installation on macOS). However, after installing and running the app on an iPad, the driver does not show up in Settings->General, nor in the app-specific settings pane triggered by the inclusion of a settings bundle in the app.

I've confirmed that the dext is indeed being included in the app bundle when built for iPadOS (in MyApp.app/SystemExtensions/com.me.MyApp.MyDriver.dext). I also can see in the build log that there's a validation step for the dext, and that seems to be succeeding.

I don't know why the driver isn't being discovered -- or in any case surfaced to the user -- when the app is installed on the iPad. Has anyone faced this problem and solved it? Are there ways to troubleshoot installation/discovery of an embedded DriverKit extensions on iOS?

Update after further debugging:

I've decided to try to get Apple's DriverKitUserClientSample sample app working on iOS, since some version of that is what was shown in the WWDC video, and it's much simpler than my driver.

I'm able to get it working on macOS, following the instructions for provisioning etc. in the page on the sample app. But I'm having the exact same problem on iPadOS where the app runs fine, but the driver doesn't show up in either general settings, nor the app's own settings page. I'm using manually, explicitly generated App IDs and provisioning profiles for the driver and container app.

Looking at the console logs on the iPad, the only thing I see that seems to have anything to do with the driver (as opposed to the container app) is this line:

debug   15:35:10.872075-0700    installd    open(/var/installd/Library/Caches/com.apple.mobile.installd.staging/temp.3XF4J5/extracted/DriverKitSampleApp.app/SystemExtensions/com.openreelsoftware.dext-to-user-client.driver.dext/Info.plist,0x0,0x1b6) = 4

Not sure what that means, except that I worry that = 4 is an error code. Assuming it's the regular open() being used here, 4 is EINTR // Interrupted system call.. Not sure if that really means anything.

I've put my modified version of Apple sample project on GitHub here: https://github.com/armadsen/CommunicatingBetweenADriverKitExtensionAndAClientApp

Any help is most welcome.