Well… 
I purge all my install from PPA, GIMP…
I download the AppImg. It’s OK. But…
NO G’MIC !!!
I took this file : https://github.com/aferrero2707/gimp-appimage/releases/download/continuous/GIMP_AppImage-release-2.10.8-withplugins-x86_64.AppImage
I really don’t understand…