Since a while PhotoFlow is also available in the form of a GIMP plug-in. It means that PhotoFlow can be used directly within GIMP, to open and process RAW images as well as to apply non-destructive editing to any GIMP layer.
The most simple way to use GIMP in combination with the PhotoFlow plug-in under Linux is to download and run the AppImage package that is hosted on the pixls.us web site. This screencast explains the details of how to run the GIMP AppImage and briefly introduces the tools that are provided with it.
One of the possibilities offered by the PhotoFlow GIMP plug-in is to apply non-destructive edits in Lab colorspace to any GIMP layer. The Lab colorspace (or better CIELab) is an alternative representation of the pixel data that, unlike RGB, separates the luminance information from the color information. It is therefore possible for example to adjust the luminance of the image without changing the color components, or to adjust the color saturation in a way that is more natural and pleasing than in RGB.
Let's see how this works in practice.