Operating system: MacOS Mojave
Graphics card: AMD
Broken: 2.80 Beta 9149e894210 2018-12-16
Using a Veikk A50 Tablet setup with Blender 2.80, the Grease Pencil always defaults to the Eraser tool despite the pen being setup to be Left Click and the settings in user preferences being setup for Left Click. Also the Grease Pencil Draw is set for Mouse -> Left Click as well in the Input settings.
Worse as expected with the TrackPad on the Mac. All other Left Click features (select object etc) work as expected with the Pen.
Exact steps for others to reproduce the error
With a Veikk A50 connected open blender 2.80
File -> New -> 2D Animation
Select Draw Pencil
Try to draw with Pen
Lines are drawn
Eraser Tool is used.