When using "best practices" and eliminating any error/warning from the build, some remain that qtcreator create; This warning is quite anoying with an otherwise clean build. One cannot simply uncheck the (depricated) option in the GUI builder as it is automatically checked/unchecked depending on which dock widget features you check. For example, checking DockWidgetClosable, DockWidgetMovable and DockWidgetFloatable automatically checks AllDockWidgetFeatures (which is depricated and generates the warning during build)

....Desktop_Qt_5_15_2_GCC_64bit-Release/ui_mainwindow.h:256: warning: ‘QDockWidget::AllDockWidgetFeatures’ is deprecated [-Wdeprecated-declarations]
In file included from ..