From LibreOffice 6.2, KDE5 and Qt5 VCL plugins are implemented and now they supports Qt IM Module, which was not available for KDE4 VCL plugin. However, the implementation of LO 6.2 is not complete. On LibreOffice 6.3, Qt IM Module works fine, as far as I tested. Tumbleweed now provides LO 6.3, so OOO_FORCE_DESKTOP is not necessary anymore. About Leap, we will need to wait until 15.2. gcin also does not need export OOO_FORCE_DESKTOP.