Here we are close to three years later and v2 has been out for a while.
No sign of a dark android theme, at least I can't find it in the 'Appearance' options?
At least the widget supports it.
I find a dark background to be much more comfortable and set my phones theme and apps this way.
As indicated by CK Portable it's also useful for night time use.
It's disappointing that this hasn't been implemented yet.
Most of the good quality apps I use these days have at least one dark and light theme.
I know this is an extra beyond basic functionality, but it's this kind of thing that sets the quality apps apart.