Good I finally did find it out. If you bring your custom driver the service needs to start before `middlewared.service`.
But to start before `middlewared.service` you can not relay on the `systemd-sysext.service`.
So I will update the blog post in the next days with my findings 🙂
I have already an idea and need to figure this out more.
For me it's important to not touch the readonly parts of truenas. And I believe that is possible, Stay tuned