Hello @jugglerchn @Eurus
In order to use qtcreator
you need to remove the current GPU packge which is for fbdev not for X11.
After install QT packages on V20191231 image. Please try the following steps to fix QTCreator issues.
khadas@Khadas:~$ sudo apt-get update
khadas@Khadas:~$ sudo apt-get -y remove linux-gpu-mali-fbdev
khadas@Khadas:~$ sudo apt-get -y install --reinstall libegl1-mesa libegl1 libgles2 libgles2-mesa libegl1-mesa-dev libgles2-mesa-dev libglvnd-dev libgles1 libwayland-dev mesa-common-dev
khadas@Khadas:~$ sudo apt-get -y install qt5-default qttools5-dev-tools qtcreator
khadas@Khadas:~$ sync
It works for me with image V20191231.