For those of us working on drivers for DriverKit, much of the example documentation is confusing, outdated, or just not an actual working example of the latest DriverKit feature set.
This post might be of some help to you.
I have published a fully working client sample app example that adds iPadOS support alongside macOS and updates to the latest driverkit version:
https://github.com/DanBurkhardt/DriverKitUserClientSample
This should be immediately runnable, but you will have to ensure you disable SIP and enable developer mode, as per the original README (this is required without DriverKit entitlement permission from Apple).
You will also need to, of course, change the bundle ID to your own name (replace "gigabitelabs" with something that is specific to your dev account / business).
Lmk if you have any issues, I'm happy to help you get this running so you can get the initial part of DriverKit testing out of the way.
Happy hacking,
Dan