The Qt4 framework has been removed from Ubuntu 20.04 main repository. It is however still required for some obsolete applications.
Though it is not recommended, you can still get Qt4 libraries (e.g.,
libqtwebkit4, and more) as software dependencies or for building an application via this third-party PPA.
1.) Open terminal either by pressing Ctrl+Alt+T on keyboard or by searching for ‘terminal’ from your system application launcher. When terminal opens, run command:
sudo add-apt-repository ppa:rock-core/qt4
Type user password (no asterisk feedback) when it prompts and hit enter.
2.) After adding the PPA, it should automatically refresh the system package cache. On some Ubuntu derivatives, you may run command to manually update the package cache:
sudo apt update
3.) Finally install the software
.deb package, and it should automatically install the required Qt4 libraries after running sudo apt -f install.
Or you may install specified Qt4 package by running command:
sudo apt install PACKAGE_NAME
See here for a full list of available Qt4 libraries.
To remove the PPA, run command:
sudo add-apt-repository --remove ppa:rock-core/qt4
To remove all Qt4 libraries, run command:
sudo apt remove --autoremove libqt4* libqtcore4 libqtgui4 libqtwebkit4 qt4*