https://gerrit.libreoffice.org/#/c/77405/ is my proposal to drop LibreOffice's Gtk2 support in favor of the Gtk3 vclplug for LibreOffice 6.4. Gtk3 has been the default for quite a while and f.e. in Fedora we dropped building Gtk2 since Fedora 30. This simplifies the ifdef maze and drops the include gtk2 source from gtk3 versions hackery