Created attachment 88474 [details] gwenview-4.14.0.log [...] -- Found JPEG: /usr/lib64/libjpeg.so [...] CMake Error at lib/CMakeLists.txt:36 (message): Unknown libjpeg version: 90 [...] Attached is the complete build.log, I've also found a patch "gwenview-4.10.2-allow-compilation-with-jpeg9.patch", source: https://projects.kde.org/projects/kdesupport/emerge/repository/revisions/a3443b2d65c234828876fe8668e09bd325586955 which still applies to gwenview-4.14.0 and allowed the build to succeed. I only did a quick test but Gwenview was able to start and view/crop/save jpeg files without any issue for me.
Fixed for 4.14.2, thanks!