pyside6 or pyqt6 ?

I am rather baffled by this….

A few years ago we developed a package using pyside1.2.4 (yes that long ago) and for various reasons have not upgraded it since then. But now we are…and moving to Python3 has been no problem but looking in the list of modules to install I am not sure which of the seemingly similar Pyqt6 or Pyside6  should be installed, or both ?

And so I tried pyside6 and that seems OK, but I can see a lot of imports have to change, however what about Designer etc. In our previous version Qt4designer was installed in linux (Xubuntu) but that does not seem to work for Qt6. So I installed the designer and tools via pip; found an issue with xub so installed that via apt and now running designer from the venv; it loads is but it doesn't respond to the keyboard/mouse.

I appreciate that this is not a Pycharm/Jetbrains issue but someone here may know about it or can point me in the right direction. I have seen several postings on the web about this (where I found the xub reference) but nothing seems to quite fit my experience.

thanks

graham