I'm trying to use the digikam quality sorter but I don't know how it works. The documentation I found that most looks like a tutorial is an almost 1-year old unaswered question on the digikam user mailing list. Has anyone ever succeeded in making it work, and if so written a small tutorial?
For the Image Quality Sorter Tool, you can use it like this:
The Image Quality Sorter assigns quality labels to images according to the settings in
Settings → Configure digiKam... → Image Quality Sorter.
There you also have to enable this tool if you want to use it. Since it is a time consuming process it's a good idea to check Work on all processor cores and restrict the job to certain albums or tags. The tool will set the red flag for “rejected”, the yellow one for “pending” and the green one for “accepted”.
Regarding the tutorial, you can find them here:
I found the documentation at the following link https://docs.kde.org/trunk5/en/extragear-graphics/digikam/index.html
and also a tutorial at the following link: https://userbase.kde.org/Digikam/Tutorials
Hope that helps!