I was trying to install WLED on a new device this week and I kept getting the error failed to execute 'open' on 'serialport': failed to open serial port when using the web installer hosted at https://install.wled.me/.
I run Ubuntu (technically Kubuntu) so it was almost certainly a permission error with the device, not a driver issue. I googled around and never really found a great answer, but I did find a workaround.

My Fix

It was as simple as changing the permissions on the device such that anyone could read or write to it.
sudo chmod 777 /dev/ttyUSB0

And with that, I hit the web installer, picked the serial port (ttyUSB0) and everything worked like a charm and I now have a fantastic new WLED controller.