So, my config is as follows:

* Running GNOME on current Rawhide
* Two displays - my laptop display (3200x1800, 100% scaling) and my desktop display (3840x2160, 125% scaling), with the desktop display on the right and set as primary, laptop display on the left as secondary
* Running a Qt5 app - Quaternion, a Matrix client

If I have the Quaternion window on the desktop display (the primary one, on the right) and wider than a certain width - it seems to be about 55% of the display width - then right-click menus appear where they should (wherever I clicked), and the app menus (Accounts, View, Room, Settings, Help) appear when I click on them, but *not* where they should - they appear way over to the right of where they should be.

If I have the window on the desktop display and narrower than that magic width, then right-click menus appear but much lower on the screen than they should, and app menus don't appear at all.

If I have the Quaternion window on the laptop display (the left one), neither right-click nor app menus appear at all.

I'm assuming this is tied in with how Plasma / Qt apps are running on Wayland by default now...