22.04 – How do I configure LXQt to show text the same size as Firefox and other applications?

I have a new installation of Ubuntu 22.04, and switched to LXQt using apt install task-lxqt-desktop. Now my 4K screen shows huge text for the LXQt applications (Qt applications?). I want the text to be similar in pixel size as the other applications like Firefox and the window titles.

What do I need to change to have them rendered similar to the firefox text?

(left == bad, right == good 🙂 )

Changing DPI setting did not have any visible effect; changing QT_SCALE_FACTOR to 2 made it worse, and 0.5 broke my UI 🙂 – note to self: don’t go below 1.0).