Empty items at beginning of list in System Settings / Window Management / Desktop Effects. Expected items appear at end of list. como 0.1.0, theseus-ship 6.0.0. X11. Both built with similar cmake options.

    -DCMAKE_BUILD_TYPE=None
    -DCMAKE_INSTALL_PREFIX='/usr'
    -DCMAKE_INSTALL_LIBEXECDIR="lib"
    -DBUILD_TESTING=OFF
    -Wno-dev

Problem goes away when kwin is installed. Returns when theseus-ship + como are reinstalled.