Please include acd10cd393abe04a8fd6fe3ab14055e09c85bc15 in QtWayland packages. This patch is needed to fix window titles. This was reported in KDE bugtracker as bug #370333 and is present in many applications. E.g. systemsettings, Plasma-Discover.
Can this issue safely be closed?
@Alexander Mentyu: The patch has been part of Qt since 5.8.0 so if you're using a newer version than that, then you already have the patch and this can be closed. Issue in Qt bug tracker: https://bugreports.qt.io/browse/QTBUG-56475