On my hardware I defined the landing page URL, so my OS shows the little prompt directly when I plug it in and when I click on it, it opens the URL. So far so good.
But now on the landing page I need to request the device manaully. navigator.usb.getDevices() returns an empty list. Wouldn't it make sense that the device is automatically connected to the webapp? Because in the end the user already did a manual selection when he/she clicked on the sytem notification..
I've considered that before but haven't checked with Chrome's security and privacy teams to see if they would consider the user clicking on the link to be a sufficient signal that the user intends to give the site full access to the device.
Can you file this on crbug.com as a feature request?