Odyssey x86j4105 ubuntu 20.4 no /dev/ttyACM0 and no seeeduino listed under lsusb

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Or if you have a Jlink around, any device that supports SWD flashing will do. The SWD pads are at the back right behind the power switch, you dont need to unmount heatsink for this.

SWD pads reference is here: