When you want to use the controller on Linux, you have to add a custom udev rule in order to give the browser permission to use the USB device.
@lezsakdomi can you please post the udev rules you added in the workshop?
During the workshop we tried the stuff that was written in webusb/arduino#29, but I'm not sure anymore which steps exactly we took and what helped in the end.
Also take a look at https://web.dev/usb/#tips