Although this should be fixed in KDE according to https://bugs.kde.org/show_bug.cgi?id=158788 although libdcraw is installed, RAW support in Kubuntu seems to be broken, eventually because: --- Comment #12 from Martin Kyral <sine.nomine@centrum.cz> --- Unfortunatelly, many distributions pushed KF5 version of gwenview before digikam folks ported libkdcraw to KF5 - which happened in the 15.12 release. Thus, they are shipping gwenview with feature regression. Please, file a bug against your distribution. Reproducible: Always Steps to Reproduce: 1. open gwenview 2. navigate to folder containing RW2 files 3. Actual Results: no preview of RW2 files Expected Results: preview of RW2 files Kubuntu 15.10 (updated against http://ppa.launchpad.net/kubuntu-ppa/ppa/ubuntu) gwenview version 15.08.3 KDE Frameworks 5.18.0 Qt 5.5.1 (kompiliert gegen 5.5.1)
I think it is safe to close this bug now. libkdcraw-enabled version of kf5 is hanging around for quite some time.
Yes, you need the KF5 version of the kdegraphics thumbnailers.