I was able to replicate the problem on Xfce. Specifically, there are two issues.
1. Dialogs are not being constrained to the available desktop real estate.
2. The Requests dialog cannot be resized.
I spent some time playing with Qt's various sizing options, but none of them made any difference in Xfce's behavior.
https://doc.qt.io/qt-6/qsizepolicy.html
That wasn't really surprising, as the current settings already create a window of any size up to the specified size constrained in the available screen real estate.
In regards to the second problem, I have no idea why the Requests dialog cannot be resized. It is created in the same was as the other dialogs that can be resized, like Settings.
I did some further testing on a number of desktop environments with the following results.
Five desktop environments exhibited no problems:
- KDE
- GNOME
- GNOME Flashback
- Cinnamon
- MATE
Three desktop environments exhibited problem 1, where the dialogs were not constrained within the available screen real estate:
Two desktop environments exhibited problem 2, where the Requests dialog could not be resized:
I found it interesting that LXDE exhibited problem 1 but not problem 2, leading me to believe the underlying cause is slightly different between them.
I found it even more interesting that LXQt had problems, as it is based on Qt (and thus I would assume it would handle Qt's window sizing system well).
But, in the end, the fact that the majority of desktop environments, including those based on GTK, did not have any problems leads me to believe this is not a bug in Privacy Browser, but in Xfce itself. As such, I would recommend you file a bug report with them.