Maybe other option would be to manually download .deb packages from 18.04 and install them on 20.04?
I doubt it's that easy when Qt4 depends on lots of specific library version.
Qt4 already each end of life, so Ubuntu 20.04 or other more recent linux distro no longer include Qt4 on their repository. You could add third party repository such as ppa:rock-core/qt4[1], but there's no guarantee you won't face another problem. Alternatively, setup a VM or Docker image which contain older linux distro, then compile the application inside it.
[1] https://launchpad.net/~rock-core/+archive/ubuntu/qt4/+packages
thanks ,i use this link https://askubuntu.com/questions/1234786/qt4-libqt4-in-ubuntu-20-04 .can it be ok?[1] https://launchpad.net/~rock-core/+archive/ubuntu/qt4/+packages
What exactly do you mean by ok? On security side, i did not find any report that repository contain dangerous binary. But i don't know whether it'll work since i haven't try it myself.
