I've installed the latest version of the Arduino IDE (1.8.4) following the instructions on the Adafruit website here:
https://learn.adafruit.com/adafruit-arduino-ide-setup/linux-setup
I connect my Pro Trinket board, but the Port menu is disabled, so I am unable to communicate and download a sketch.
I've also tried to run Arduino as root with gksudo, but I get the error:
(gksudo:6222): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",
Suggestions?