Great read, I definitely agree that Web USB and Web Bluetooth are game changers when you want to build connected hardware. Another approach for connecting CDC devices would be to use NW.js together serialport npm module. As NW.js is built on top of Chromium, this mean you can build your UI with all modern web technologies, just as if you were a web page running inside chrome. I tried this approach with in one of my Arduino projects, and it works like a charm (tested both on Windows 10 and Ubuntu).

Anyway, seems like USB CDC is very common nowadays. Perhaps we should also aim to have a WebSerial standard? This should get us covered for USB CDC as well as Serial Bluetooth devices.