pianu.com used to be a website where you could learn piano by connecting your piano through usb with the browser. It seems defunct now but I found a video demonstrating it : https://www.youtube.com/watch?v=kTBmRV02NgI

I used something similar in the past. It was a legitimate use case for web usb which changed my mind on it quite a bit.

https://www.charachorder.com/ sells ergo keyboards and allows you to update their firmware directly in the website, through web usb. No local apps at all. Also an improvement in overall security from having to download some .exe / .dmg and running it locally.