Description:
I get the message: avrdude: ser_open(): can't open device "/dev/ttyUSB1": Permission denied
And if I do: "sudo chmod a+rw /dev/ttyUSB1" it works. My user though, is inside uucp group, so the chmod part shouldn't be needed. There is something wrong.

$ ls -l /dev/ttyUSB1
crw-rw---- 1 root uucp 188, 1 Dec 8 19:43 /dev/ttyUSB1

Additional info:
$ pacman -Q | grep arduino
arduino 1:1.8.16-1
arduino-avr-core 1.8.3-1
arduino-builder 1.6.1-1
arduino-cli 0.19.3-1
arduino-ctags 5.8_arduino11-4
arduino-docs 1.6.6-7