Long, long ago, in a land far, far away.
QtDesigner was installed.
sudo apt-get install qt4-designer libqt5designer5 python3-pyqt5 python3-pyqt4 libqt5sql5-sqlite
I'm focusing on Python3 & PyQt5 with a sqlite3 backend. Python3 & sqlite3 seem plenty mature enough, well documented & plenty of examples. PyQt5 I'm unsure about at this stage.
Have had a play with Kivy & found it wasn't quite what I was looking for. I'm looking for click & drag, point & click type, high-level interface.
Had a play with GTK+3. Used Glade, got the proof of concept done. But, it was hard work! Bumped in to lots of comment that "others" were porting to Qt. I.E.
I run Xfce4 which is GTK+2 based at this time, so I would have loved to keep it native. But I want it to work, not build a better mousetrap.
So off I went.