When it comes to RAW editting sotware with Linux things are pretty dull in Linux.
There is lots of software like Adobe Camera Raw and Lightroom that are industrial standard, but unfortunately not working in Linux.
What were the options? For a long time there were no usable RAW editting software. There were converters and cmdline utilities, but these things were more developer-oriented than photographer-friendly. Until recently when Darktable emerged from the dark. It truned out to be very nice app with LR-like interface and tons of image settings. It is actively developed software whit new versions comming every month, providing lots of new features.
So, what is the problem with Darktable? It is very young application with not so big user base. Photographers preferred to work with Windows or Mac because of the mentioned lack of Linux software, and that is going to keep on for a while. Currently there is a deficiency of tutorials and helping readings. There are couple of video tutorials in YouTube, but 99% of these are in non-english language. When it comes to written articles, there is the User Manual that is very decent, but it is not a tutorial.
That's why I decided to start a tutorial section here. It is going to be a series of short articles explaining how I have achieved this or that effect and I hope more people will get into Darktable. It will not be a "For dummies" one, explaining how to click the mouse and how to move a slider You'd better have the User manual first.