[avianlyric]

Well according to the article the entire firmware flashing process does happen over USB. The website is just a JS executable that uses WebUSB API to perform the flashing process via a browser.

As is also mentioned in the article, the author reverse engineered the site, and create a python script capable to performing the flashing process via standard OS APIs.

Really the flashing site isn’t really “a site”. It’s a hosted executable written in JS that pretty much runs entirely locally, apart from the bit where it downloads the new firmware to be flashed. It should be possible to extract the JS itself, plus firmware blobs, and run that completely offline for as long as browsers support WebUSB. Or you do what the author did and create a Python equivalent.