This device shows up as a keyboard - should keyboards never be trusted ever? How would that work?
Going back to PS/2 could be an option? Guess that wouldn't be too different from allowing all devices only on a single USB port.
Any desktop computer would have to be redesigned to add a "allow new device" button since they have no other input.
Even on many laptops, the internal keyboard and mouse are USB devices, when you install a new OS, do you have to accept trust to those as well? Or how will you stop an external device from spoofing them with the same vendor/device ID?
This sounds like something that creates a chicken-and-egg problem of there not already being any such DTLS-speaking USB devices... but how about if vendors just create a little USB dongle that wraps whatever's plugged into it in "authentication" using DTLS? Ship the dongle with the laptop; tell people that if they want to install a new OS, they have to plug a USB keyboard in through the dongle.
hell, simply through acquisition and acquiescence, the market already accepted locked-down platforms. at this point, we ought to have more benefits from this instead of just making these platforms hard to install Linux on.
Or only allow completely unauthenticated devices as a fallback when there is no other available authenticated device.
A computer not having any keyboard is a rare case. Most of the time you have what is built-in (and should be authenticated) or what came with the computer (and should be authenticated).
Allowing unauthenticated keyboards only on detection of no authenticated ones probably covers 99.9% of all use cases and increases security dramatically.
Not sure if I just mis-configured my windows, but it is certainly lacking on that front. The Settings -> Devices -> USB having just a single checkbox for error popups is probably not a good sign.
Usability could be optimized depending on how uniquely identifiable keyboards are (to reduce when trust prompts are shown).