http://gambaswiki.org/bugtracker/edit?object=BUG.1928&from=L21haW4- Comment #6 by Gianluigi GRADASCHI: Sorry yesterday I was too sleepy :-( export GB_GUI=gb.qt5 && gambas3 Works well I confirm that in Ubuntu 20.04 'export GB_GUI=gb.gui.qt' does not work due to missing qt4