Message “WebUSB not available” when using Firefox, even in Safe Mode. Chrome works and programs properly. So does Microsoft Edge.
This is a known issue. Firefox does not support web usb at this time.
Interesting to know Edge works, though.
Edge is running the chrome engine under the hood, so it supports everything chrome does – including webUSB, webMIDI, etc.
Someone has to write the code for it, with firefox.