After comparing further I found out the following files are actually missing in the French flavour :
baloomonitorplugin.mo
bluedevil.mo
customtoolsplugin.mo
elfutils.mo
gnupg2.mo
gom.mo
json_kdeedu_artikulate.mo
json_kdeedu_cantor.mo
json_kdenetwork_krfb.mo
json_kdenetwork_ktp-common-internals.mo
json_pim_kdepim-addons.mo
kaddressbook_plugins.mo
kate-replicode-plugin.mo
kdeconnect-cli.mo
kdeconnect-core.mo
kdeconnect-fileitemaction.mo
kdeconnect-kcm.mo
kdeconnect-kded.mo
kdeconnect-kio.mo
kdeconnect-plugins.mo
kexixbasedriver.mo
kmail_plugins.mo
kscreenlocker_greet.mo
kscreenlocker.mo
ksshaskpass.mo
kterustcompletion.mo
libkirigamiplugin_qt.qm
liboxygenstyleconfig.mo
libpurpose_quick.mo
libpurpose_widgets.mo
messageviewerheaderplugins.mo
messageviewerplugins.mo
oxygen_style_config.mo
oxygen_style_demo.mo
phodav-2.0.mo
plasma_applet_org.kde.kdeconnect.mo
plasma_applet_org.kde.plasma.bluetooth.mo
plasma_applet_org.kde.plasma.mediaframe.mo
plasma_applet_org.kde.plasma.minimizeall.mo
purpose_imgur.mo
purpose_ktp-sendfile.mo
purpose_pastebin.mo
purpose_saveas.mo
purpose_youtube.mo
screenlocker_kcm.mo
tabswitcherplugin.mo
texinfo_document.mo
texinfo.mo
user_manager.mo