When you have your tag in clipboard, simply pasting it into the album view "add face" overlay does not enable the "confirm button", nor the "enter" action. You have to type something (space+backspace, for example) and then you can submit with the "enter" key or the "confirm" button.
Works normal here, also under Kubuntu but with digiKam 5.4.0.
Do you have an AppImage for 5.4.0 to test?
5.4.0 test AppImage : https://drive.google.com/open?id=0BzeiVr-byqt5Y0tIRWVWelRJenM Gilles Caulier
Stephano, Did you try with current development AppImage bundle for Linux ? Gilles Caulier
Git commit 949e7bf27067af3ebb48685b31c7b58a3e57b736 by Maik Qualmann. Committed on 29/12/2016 at 11:42. Pushed by mqualmann into branch 'master'. fix completion mode for manual face tagging Related: bug 374185, bug 284780, bug 368124, bug 360155 FIXED-IN: 5.4.0 M +6 -1 NEWS M +40 -2 libs/tags/addtagscombobox.cpp M +8 -0 libs/tags/addtagscombobox.h M +7 -3 libs/tags/tagscompleter.cpp M +10 -0 utilities/facemanagement/assignnamewidget.cpp M +2 -0 utilities/facemanagement/assignnamewidget.h M +9 -1 utilities/facemanagement/facegroup.cpp https://commits.kde.org/digikam/949e7bf27067af3ebb48685b31c7b58a3e57b736