qt4 dropped on Ubuntu 20.04, Qfsm needs port to qt5

[AaronErhardt]

qt4 is no longer available for Ubuntu 20.04, which means that Qfsm no longer works with the latest Ubuntu releases. graphviz is not affected by this change.
There seems to be no reasonable workaround for this problem so far, so the best solution would be to port Qfsm to qt5 (which has been around since 2012!!) or even directly to qt6 which will be released in a few months.
Anyway, I don't have time to solve this right now (nor do I have a lot of experience with qt), so any help would be much appreciated :)

[AaronErhardt]

As a short term solution I have added an AppImage package to the latest release that works across all modern Linux distributions. This doesn't change the fact however that Qfsm needs to be ported to newer requirements in future - qt4 will die out sooner or later.
I hope we can soon start porting Qfsm to newer requirements soon. And as always: any help in this direction would be much appreciated :)