(Apologies if this is in the wrong category; it's not clear to me where it should go.)
i've been doing some stuff on an Arduino Uno R3 for the last few weeks on my Manjaro computer, and today when I plugged it in, I discovered that my computer is no longer recognising it. arduino-cli list boards says no boards are connected, and there is no /dev/ttyUSB0 device any longer (ls /dev only shows tty0 through tty63 and ttyS0 through ttyS31). The L and ON LEDs are on, and RX is flashing.
What do I need to do to get my system to recognise the board again?
The behaviour of L LED depends on the code that you loaded. If the RX LED is flashing without you sending data, I suspect that the serial-to-usb converter is damaged. What is your project about?
First things to check is lsusb and dmesg (or dmesg -w) to see what the operating system thinks of the board.
Although it's not very obvious, avrdude, stk500, bootloader issues is the more suitable one; hence topic moved.
I think this may have been an unrelated issue, since I discovered I was having issues with a gamepad also not having its device created properly. After a reboot, /dev/ttyUSB0 was properly created on plugging the device in.